... and one more question:
The tables created by version 2.4.24 use utf8_general_ci throughout, not utf8mb4
name varchar(255) utf8_general_ci
Do I have to change every collation to utf8mb4 in the database manually, or will this be done by update_188.8.131.52-2.5.php?
This is one of the tasks, the update script is performing.
Unfortunately there are currently a few pitfalls in the update script, that are caused by MySQL-server-configurations we wasn't aware of and wasn't be able to test before the releases of the first versions of the 2.5-branch (20220508.1 and later). We have to solve these issues first, before we can recommend an upgrade to the 2-5-branch for forum operators, who are not really familiar with PHP, MySQL and the code of the forum script to inspect and possibly solve issues themselfes.
Trenne niemals Müll, denn er hat nur eine Silbe!