LND has signet support in latest beta, just got it up and running, tho not many nodes out there yet.
You have to enable it first by placing
bitcoin.signet = true in the lnd.conf file.
According to
lnd PR #5025, it's reusing mainnet's DNS seeds for Signet, which partially explains why there are hardly any signet nodes to connect to - Bitcoin Core itself only has a few of them listening for connections.