It would be nice to have documentation on how to set up a basic M-of-N multisig between multiple people using descriptor wallets and PSBTs, as well as a signing flow.

E.g. (borrowed some steps from @jonasschnelli)

• First phase: generate and exchange xpubs:
  • Every participant generates an xpub: most straightforward is to create a new wallet, I guess, but how to get the xpub to share for a specific BIP32 path?
  • Maybe wallet: listdescriptors uses normalized descriptor form #21277 helps here but it might be putting the cart before the horse: do we want the default non-multisig descriptors at all here? I don't think so.
  • Share it with the other participants.
• Second phase: Every participant imports the following descriptors using importdescriptors:
  • Receiving (internal: false) addresses are wsh(sortedmulti(<M>,xpubA/0/*,xpubB/0/*,xpubC/0/*,…))
  • Change (internal: true) addresses are wsh(sortedmulti(<M>,xpubA/1/*,xpubB/1/*,xpubC/1/*,…))
• Send funds to the resulting address (every participant should get the same addresses).
• When making a sending transaction create one using walletcreatefundedpsbt (everyone can initiate this)
  • Send the resulting PSBT to other users
  • At least M users checks it with decodepsbt then (if ok) signs it with walletprocesspsbt
  • Collect the signed PSBTs with joinpsbts then broadcast the resulting transaction