You folks seem to all be running the 11.1.0 version for YunoHost, which is the infamous “YunoHost 11.1.x (testing) was incorrectly released on the stable channel instead of testing”
You should be running instead 11.1.2.x (testing) at least, which is more consistent with the fix published on SSOwat (it adds the use_remote_user_var_in_nginx_conf flag)
So I would advise using
curl https://install.yunohost.org/switchtoTesting | bash
to enable testing, to at least just to upgrade to 11.1.2.x, and then if you want remove the “testing” keyword from /etc/apt/sources.list.d/yunohost.list (though honestly I would advise keeping the testing channel enabled until we release 11.1 as stable …)
The alternative can be to downgrade ssowat but honestly meh, not even sure that’s easily possible