Comment # 1 on bug 1220301 from Stefan Hundhammer

This is possible even now, and has been possible since YaST exists (i.e. since
late 1999).

Probably the standard storage proposal won't do that for you since it's a very
nonstandard setup. It will work for sure with the expert partitioner, and maybe
also with the guided storage setup (but I haven't tried that).

It's very simple to create the necessary partitions, including the root
partition, a swap partition that is not shared with any other OS on that
machine, your separate /home, and whatever else you might want. What's the
problem with that?

I don't know what you mean with "its own UEFI"; do you mean the ESP (Efi System
Partition)? AFAIK there can be only one on a machine, and that is defined by
the EFI standard; this is where the EFI bootloader lets you select what OS to
boot. You can't have more than one of them.

As a YaST developer since 10/1999 I have constantly been installing multiple
instances of SUSE Linux, Ubuntu, Windows and whatever in parallel on the same
machine; on one disk, on multiple disks, in all kinds of permutations. I am
doing this on a regular basis, and I have done that with at least a dozen
machines over time.

So, what exactly is it that you are missing?

What makes you think you have to physically disconnect any disks to achieve
this?

I think you are making this artificially overcomplicated; you might be
overthinking the problem. Maybe take a step back and simply try again without
confusing yourself.