It's not just Boltz, there's others too. (Sideswap, side shift). Also you don't have to rely on them either, anyone can peg-in to liquid using on-chain Bitcoin using the liquid node software, Elements. There's Peerswap that you can swap on-chain, lightning, and liquid in a p2p fashion too.

Liquid is great 👍 the federation risk of liquid complements the hot wallet risk of lightning nicely. For example when one swaps outbound lightning liquidity for L-BTC, that balance can be taken offline