I offer taking BTC or LTC with a 10-15% discount, both either on chain or through the LN.

Sometimes, someone asks if I take stablecoins or ETH. I tell them I would, but with a 50% and a 100% premium, respectively, which they always refuse, of course. I then suggest they send them over the RSK network using a decentralized bridge, where I'd take them with just a 25% or 50% premium, respectively. Once they know that, they either go the whole way to convert them to BTC and pay me with it, or don't bother and give me cash.