Boltz is a privacy-first account free exchange and a Lightning Service Provider. By doing a Reverse Submarine Swap on Boltz, you can swap your Lightning Bitcoin for on-chain Bitcoin.
Step 1: Deciding to Reverse Submarine Swap
You have one or more channels that are running low on inbound capacity or you want to move some of your Lightning Bitcoin to your onchain wallet.
Step 2: Paying the Lightning Invoice
Your Boltz client generates a secret which is sent to Boltz. In return Boltz sends a Lightning invoice based on that secret. Your Lightning node pays that invoice which moves some of your local balance to the other side of the channel.
Step 3: Receiving the funds on-chain
In return for paying the invoice, Boltz locks on-chain BTC. Your node claims that onchain BTC to your wallet and by doing that, reveals the secret. With that secret Boltz can settle the Lightning invoice paid by your node.
Done!
You have now successfully received your funds in your on-chain wallet and also spent your local balance to increase the inbound capacity of your node - all in a non-custodial manner.