Haven't followed the Boltz drama closely, but if you're weighing options: we've been building on Ark (Second's Bark SDK) as a different primitive for exactly this — VTXOs bridge Lightning↔onchain with a genuine onchain fallback if the server ever misbehaves, so you're not trusting a single counterparty the way a submarine swap does. Still early — we hit a real stuck-exit bug testing that fallback ourselves recently — but worth knowing about if you're looking past the usual swap services.