After a long time whishing to set up my own XMPP-Server I finally found the time to do it.
After a little investigation I settled on Prosody as the server. Check the project homepage for great documentation on the project itself and even most related stuff like XEPs etc. Brcause this great resource is available I won't try to replicate that but just compile my results from there, mostly to remind me about my own configuration in case I need to revisit it.
So, follow along to see my setup...
First configure DNS entries for A-Record, SRV Records for server and client as well as SRV Record for conference-subdomain.
Obtain a LetsEncrypt-Certificate for all relevant domains
Password storage