unwanted setlocale() interaction between mod_php and mod_perl2

Hi!

Up until Ubuntu 18.04 LTS or Debian 9, a perl service (eprints.org) and a PHP service (nextcloud) worked smoothly next to each other on Apache with mod_php and mod_perl2.

However, on Ubuntu 20.04 LTS, or Debian 10, as soon as I enable mod_perl2, setlocale() on nextcloud does not seem to work anymore.

The relevant versions are

Apache 2.4.29 and mod_perl2 2.0.10, mod_php7.2 7.2.24 vs.
Apache 2.4.41 and mod_perl2 2.0.11, mod_php7.4 7.4.3

This issue is already documented at least in two locations that I know of:

https://bugs.php.net/bug.php?id=81596
https://bugs.mageia.org/show_bug.cgi?id=25411

The first one states that setlocale() in PHP does not work anymore globally, so this does not seem to be a nextcloud specific issue, but some kind of general interaction problem, as it seems mod_perl2 somehow manipulates the process' locale in an unchangeable way.

I tried hard to find a bug tracker for mod_perl2 but have not been successful till now, so please excuse if there is one and this is already documented (and please give me a link)!

Any insight is appreciated.

Thanks in advance!
th