This is a draft answer (incomplete).
To get set up on Signet ie sync the Signet chain and claim some Signet Bitcoin, follow these instructions. (You can run a Signet node in parallel with your mainnet node, ie same hardware)
You now have funds at a non-P2TR (i.e. SegWit v0) Signet address. Now you need to generate a P2TR address to send funds to so you have funds at a P2TR address (so you can spend from it).
TBC