Good evening,
I switched back to php 7.4: it works ;)
My http server is nginx and it is possible to do without .htaccess (which is indeed specific to apache).
In the web folder of the forum, I copy the configuration file because I will not use the .htaccess file with nginx:
cp config.default.php config.php
In this file, we specify the folder containing the users information:
``@define ('FORUM_USERS', '../forum_users');``
In direct url access, this works perfectly. But my reverse proxy is also nginx and I'm still looking for it: If I find it, I'll come back to indicate a solution :)
Thanks to both of you, greetings from France !
Translated with www.DeepL.com/Translator (free version) because je suis nul en anglais :)