Also a concern is setting the value dynamically:

I installed the plugin:

root@mac [(none)]> INSTALL PLUGIN clone SONAME 'mysql_clone.so';
Query OK, 0 rows affected (0.23 sec)

I modified the setting using SQL:

mysql -vvvt <<EOF
set global clone_valid_donor_list ="100.100.100.100:3306,100.100.100.100:3306,100.100.100.100:3306,100.100.100.100:3306,100.100.100.100:3306,100.100.100.100:3306,100.100.100.100:3306,100.100.100.100:3306,100.100.100.100:3306,100.100.100.100:3306,100.100.100.100:3306,100.100.100.100:3306,100.100.100.100:3306,100.100.100.100:3306,100.100.100.100:3306,100.100.100.100:3306,100.100.100.100:3306,100.100.100.100:3306,100.100.100.100:3306,100.100.100.100:3306,100.100.100.100:3306,100.100.100.100:3306,100.100.100.100:3306,100.100.100.100:3306,100.100.100.100:3306,100.100.100.100:3306,100.100.100.100:3306,100.100.100.100:3306,100.100.100.100:3306,100.100.100.100:3306,100.100.100.100:3306,100.100.100.100:3306,100.100.100.100:3306,100.100.100.100:3306,100.100.100.100:3306,100.100.100.100:3306,100.100.100.100:3306,100.100.100.100:3306,100.100.100.100:3306,100.100.100.100:3306,100.100.100.100:3306,100.100.100.100:3306,100.100.100.100:3306,100.100.100.100:3306,100.100.100.100:3306,100.100.100.100:3306,100.100.100.100:3306,100.100.100.100:3306,100.100.100.100:3306,100.100.100.100:3306,100.100.100.100:3306,100.100.100.100:3306,100.100.100.100:3306,100.100.100.100:3306,100.100.100.100:3306,100.100.100.100:3306,100.100.100.100:3306,100.100.100.100:3306,100.100.100.100:3306,100.100.100.100:3306,100.100.100.100:3306,100.100.100.100:3306,100.100.100.100:3306,100.100.100.100:3306,100.100.100.100:3306,100.100.100.100:3306,100.100.100.100:3306,100.100.100.100:3306,100.100.100.100:3306,100.100.100.100:3306,100.100.100.100:3306,100.100.100.100:3306,100.100.100.100:3306,100.100.100.100:3306,100.100.100.100:3306,100.100.100.100:3306,100.100.100.100:3306,100.100.100.100:3306,100.100.100.100:3306,100.100.100.100:3306,100.100.100.100:3306,100.100.100.100:3306,100.100.100.100:3306,100.100.100.100:3306,100.100.100.100:3306,100.100.100.100:3306,100.100.100.100:3306,100.100.100.100:3306,100.100.100.100:3306,100.100.100.100:3306,100.100.100.100:3306,100.100.100.100:3306,100.100.100.100:3306,100.100.100.100:3306,100.100.100.100:3306,100.100.100.100:3306,100.100.100.100:3306,100.100.100.100:3306,100.100.100.100:3306,100.100.100.100:3306,100.100.100.100:3306,100.100.100.100:3306,100.100.100.100:3306,100.100.100.100:3306,100.100.100.100:3306,100.100.100.100:3306,100.100.100.100:3306,100.100.100.100:3306,100.100.100.100:3306,100.100.100.100:3306,100.100.100.100:3306,100.100.100.100:3306,100.100.100.100:3306,100.100.100.100:3306,100.100.100.100:3306,100.100.100.100:3306,100.100.100.100:3306,100.100.100.100:3306,100.100.100.100:3306,100.100.100.100:3306,100.100.100.100:3306,100.100.100.100:3306,100.100.100.100:3306,100.100.100.100:3306,100.100.100.100:3306,100.100.100.100:3306,100.100.100.100:3306,100.100.100.100:3306,100.100.100.100:3306,100.100.100.100:3306,100.100.100.100:3306,100.100.100.100:3306,100.100.100.100:3306,100.100.100.100:3306,100.100.100.100:3306,100.100.100.100:3306,100.100.100.100:3306,100.100.100.100:3306,100.100.100.100:3306,100.100.100.100:3306,100.100.100.100:3306,100.100.100.100:3306,100.100.100.100:3306,100.100.100.100:3306,100.100.100.100:3306,100.100.100.100:3306,100.100.100.100:3306,100.100.100.100:3306,100.100.100.100:3306,100.100.100.100:3306,100.100.100.100:3306,100.100.100.100:3306,100.100.100.100:3306,100.100.100.100:3306,100.100.100.100:3306,100.100.100.100:3306,100.100.100.100:3306,100.100.100.100:3306,100.100.100.100:3306,100.100.100.100:3306,100.100.100.100:3306,100.100.100.100:3306,100.100.100.100:3306,100.100.100.100:3306,100.100.100.100:3306,100.100.100.100:3306,100.100.100.100:3306,100.100.100.100:3306,100.100.100.100:3306,100.100.100.100:3306,100.100.100.100:3306,100.100.100.100:3306,100.100.100.100:3306,100.100.100.100:3306,100.100.100.100:3306,100.100.100.100:3306,100.100.100.100:3306,100.100.100.100:3306,100.100.100.100:3306,100.100.100.100:3306,100.100.100.100:3306,100.100.100.100:3306,100.100.100.100:3306,100.100.100.100:3306,100.100.100.100:3306,100.100.100.100:3306,100.100.100.100:3306,100.100.100.100:3306,100.100.100.100:3306,100.100.100.100:3306,100.100.100.100:3306,100.100.100.100:3306,100.100.100.100:3306,100.100.100.100:3306,100.100.100.100:3306,100.100.100.100:3306";
EOF

and then checked the resulting value which is clearly truncated and generates no error:

$ mysql
Welcome to the MySQL monitor.  Commands end with ; or \g.
Your MySQL connection id is 10
Server version: 8.0.23 MySQL Community Server - GPL

Copyright (c) 2000, 2021, Oracle and/or its affiliates.

Oracle is a registered trademark of Oracle Corporation and/or its
affiliates. Other names may be trademarks of their respective
owners.

Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.

root@mac [(none)]> show global variables like 'clone_valid_donor_list';
+------------------------+------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| Variable_name          | Value                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                            |
+------------------------+------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| clone_valid_donor_list | 100.100.100.100:3306,100.100.100.100:3306,100.100.100.100:3306,100.100.100.100:3306,100.100.100.100:3306,100.100.100.100:3306,100.100.100.100:3306,100.100.100.100:3306,100.100.100.100:3306,100.100.100.100:3306,100.100.100.100:3306,100.100.100.100:3306,100.100.100.100:3306,100.100.100.100:3306,100.100.100.100:3306,100.100.100.100:3306,100.100.100.100:3306,100.100.100.100:3306,100.100.100.100:3306,100.100.100.100:3306,100.100.100.100:3306,100.100.100.100:3306,100.100.100.100:3306,100.100.100.100:3306,100.100.100.100:3306,100.100.100.100:3306,100.100.100.100:3306,100.100.100.100:3306,100.100.100.100:3306,100.100.100.100:3306,100.100.100.100:3306,100.100.100.100:3306,100.100.100.100:3306,100.100.100.100:3306,100.100.100.100:3306,100.100.100.100:3306,100.100.100.100:3306,100.100.100.100:3306,100.100.100.100:3306,100.100.100.100:3306,100.100.100.100:3306,100.100.100.100:3306,100.100.100.100:3306,100.100.100.100:3306,100.100.100.100:3306,100.100.100.100:3306,100.100.100.100:3306,100.100.100.100:3306,100.100.100.100: |
+------------------------+------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
1 row in set (0.01 sec)

root@mac [(none)]>