To avoid it? Don't use BlueWallet for LN. It's one of my favourite Bitcoin on-chain wallets but the Lightning part is custodial unless you connect your own node. But even after that, they charge pretty high fees for large transactions. On small transactions (like a few hundreds or thousands sats) it doesn't really matter and the fees are pretty low it's just about large txs.

I'm also surprised why Francis isn't using on chain for this (I'm guessing) large amounts.