The issue is definitely about
Apr 11 18:40:01 artanux.be systemd[1]: Starting nginx.service - A high performance web server and a reverse proxy server...
Apr 11 18:41:31 artanux.be systemd[1]: nginx.service: start-pre operation timed out. Terminating.
Apr 11 18:41:31 artanux.be systemd[1]: nginx.service: Control process exited, code=killed, status=15/TERM
which i saw a few times in the past (for example here) but unfortunately is pretty fuzzy and it’s not clear to me what could be causing this in the first place (nor apparently how you managed to solve it apparently?)
The “Start-Pre” operation is apparently, according to systemctl cat nginx :
ExecStartPre=/usr/sbin/nginx -t -q -g 'daemon on; master_process on;'
which is basically just nginx -t … plus the -g option which is a bit obscure to me
Searching on Google, this article is talking about OCSP stapling but that doesn’t seem to correspond to YunoHost’s context
This thread is talking about PID=/run/nginx.pid versus PID=/run/nginx/nginx.pid (in the systemd conf) but I doubt this is the issue (why would your conf be different than anybody else and why was it working in the past..)
Soooo idk, maybe if the issue pops back up, I would try manually running the “StartPre” operation (/usr/sbin/nginx -t -q -g 'daemon on; master_process on;) to see if that command is indeed taking an unusual amount of time (more than a (few?) second)