So I tried to again to modify the same value in the config panel, and I got the same issue BUT I saw a warning that could explain it (raised when saving the config file):
The line md5sum : option non reconnue ‘–file=/var/www/nextcloud/apps/user_ldap/lib/User/User.php’ was already seen in the log I first shared.
It comes from helper ynh_store_file_checksum. I’ll see if I can investigate a little more.