I tested btc to L-USDT: Peg-in onchain btc into SideSwap to receive L-BTC (you pay standard btc miner fee + 0.1% on the swap).

Then you can instantly swap L-BTC to L-USDT.

Liquid blocks are guaranteed every minute and they consider two confirmations (so 2 minutes) as finality.

Doing everything in reverse should work, too:

* swap L-USDT to L-BTC

* peg-out back to btc

* OR use Boltz to go straight from L-BTC to your LN wallet (pretty f'n mind-blowing!).