I have separated installations of nextcloud and collabora.
Now I tried to connect my nextcloud with the collabora instance but it fails with error:
GuzzleHttp\Exception\ConnectException: cURL error 7: Failed to connect to collabora.lis.school port 443: Connection timed out
When I try to access https://collabora.lis.school/hosting/discovery everything seems to be ok.
Maybe you have got an idea what I can try next?