Triple active SIM would be amazing, but one can dream. I would love to have a phone that has an active AT&T, T-Mobile, and Verizon SIM at the same time.

You can fit several esims on one of these adapters AIUI.

https://jmp.chat/esim-adapter

i'm surprised this works, in the sense that there aren't tons of technical safeguards and/or lawsuits getting in the way of someone doing this