I have been using L-BTC (liquid) and I would like to suggest you to add this 2nd layer solution to your services. I would certainly use it and I believe other members would use it as well.
I am also supporting this suggestion.
Exch alreadx supports Lightning Network so adding Liquid would be cool, both for L-BTC and for L-USDT, especially for people who don't want to mess with shitcoins and still use stable coins.
Only thing I am not sure is how they will provide enough liquidity for L-BTC and L-USDT.
Purely out of curiosity, have you tried using
https://boltz.exchange/ for Liquid swaps? It's what
Aqua wallet uses for its swap functionality. I've used Boltz before for Lightning and it worked really well.
Aqua wallet is using Boltz and SideSwap, they just merged everything into one super easy to use wallet.