Open XUMM and turn on developer mode to clearly see what XRPL network you are connected to.
Settings -> Advanced -> Developer Mode
Open XUMM and scan the QR code below. Please note this is the only possible way to connect to the devnet by scanning this QRcode.
To then connect to the XRPL NFT-Devnet, please follow these steps carefully.
Settings -> Advanced -> Node -> Custom -> xls20-sandbox.rippletest.net:51233
NOTE: This will mean you cannot see funds in your Mainnet Wallets, YOU HAVE NOT LOST YOUR FUNDS To change back to the mainnet and conduct normal transactions there, please go
Settings -> Advanced -> Node -> Main net -> wss://xrplcluster.com
You can now interact with the NFT-Devnet using you XUMM wallet.