Connect UCS to public domain

Hi everyone, here is what I want to do:

  • I have a server with a public IP address, where I want to install UCS
  • I have a public domain that I want to link to that server
  • I want to enable https connection
  • I want to connect specific apps to other domains

There are some guides on this topic (e.g. this one), but as a beginner I found them confusing. Does the fully qualified domain name that needs to be given during the installation need to match the public domain? Or can I simply point a domain to this IP address later on? And can I use let’s encrypt with just the IP address?

Thanks in advance!