So you bought an esim from a store or you were converting  the existing sim into an esim?
From your description, the trasnfer wasn't successful, have you tried to redo it?

Got eSIM in the store. When trying again I get “This eSIM has already been used” message. Phone is Samsung Galaxy S23 Ultra.

Can you remove the physical sim out of the phone and reset network settings to see if it can help?

Did you complete a sim swap in your self serve?

Removing SIM + network reset did not help.

SIM swap is probably on the track, but it doesn’t look like feature is working. This is what I have on the screen after 5 minutes of waiting.

Would SIM swap even work to eSIM, or does destination have to be SIM too?

On second attempt SIM swap screen is now working, but it says

Heads up:

Don't insert your new SIM into your new phone until the SIM-change process is complete.

Since I already tried to register eSIM will this work at all, or am I going to deregister original SIM and be left without original SIM and new eSIM?

It should only deregister your original sim if it can register your new sim.

Your phone does show your esim as available to use, just unknown and unkown number right?

That is correct. It shows eSIM and “unknown” and “unknown number” next to it.

SIM to eSIM swap in self serve successful! Thank you.