For now, I keep MySQL 5.1 in remi and MySQL 5.5 in remi-test, so users have the choice.
PHP 5.3 is build against MySQL 5.1 but can be used with compat-mysql51 (client library) beside MySQL 5.5
I a near future, I will stop build MySQL 5.1 new version and will only work on MySQL 5.5 which will go in remi repo.
MySQL 5.5.8 is the first GA version, and have a major rewrite of the spec (switch to "cmake"). I'm waiting for some feedback (even if no "bad" feedback is probably good)
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Laptop: Fedora 38 + rpmfusion + remi (SCL only)
x86_64 builder: Fedora 39 + rpmfusion + remi-test
aarch64 builder: RHEL 9 with EPEL
Hosting Server: CentOS 8 Stream with EPEL, rpmfusion, remi