2 encrypted Linux distros as dualboot

I’m always on the lookout for this type of information and have yet to see a tutorial that meets your needs, sorry.

But it can be done!
The problem is that it probably will require a lot of manual interaction (partitioning, the boot part, …) and depending on how Xubuntu sets up the encryption (encrypted or unencrypted /boot) you’ll maybe even want/need to set up a third installation just to easily choose your system at boot time.

Given your experience level, you may be in for a world of hurt.

Is Xubuntu a company, school or university requirement?
If it is just your personal preference, why not just try an encrypted EndeavourOS? Can*t imagine anything running on Xubuntu you couldn’t set up on Arch.

If you prefer LVMonLUKS there’s a tutorial here, but I would recommend you try the easier to install (~15m) beginner friendly BTRFSonLUKS setup described here.