Question: is there an chance zu run nextcloud and collabora on one server with the same domain? I’m using a fritzbox and SPDNS to get an ip-adress. If I create a second domain i have the problem to update the ip-adresse with the adress of my first domain.
It’s possible to do, but I think you’ll have better luck using a CNAME record as recommended - the Apache/nginx settings can be configured separately, and any cross-site-scripting vulnerabilities are avoided.
Your DNS provider should support creating a new CNAME (e.g. collabora.example.com) that points to the same IP as your current name (e.g nextcloud.example.com).
There’s a basic explanation here, but your DNS provider should also have more details on how to do it from their service.