In case you don't know you can already use Boltz Exchange to swap trustlessly between Liquid, BTC on-chain, BTC LN, it works pretty well.
Discussion
Thanks. I'll have a look at that
On Boltz for BTC on chain to lightning, make sure to not be too stingy on the transaction fees and also recommend making sure your invoice is set to expire not on the commonly default 60 mins. A few hours or more, depending on your fee selection, is better so that the invoice doesn't expire before the confirmation on chain has been finalised. Getting a refund for a failed attempt is a 24 hour wait. The lightning to liquid swap is super smooth and fast on Boltz though.