Bitcoin payments can be non trivial if done via Lightning network (liquidity management is not easy).
I can imagine mu.app being a LN payment processor.
Definitely, and rugpulling "payments" with "only crypto btw" also sets up a huge red flag. Most people are heavily fatigued on weird blockchain projects and looking for any excuse to nope out of this and use a more familiar definitely-not-blockchain competitor. I was wondering if this was a supabase competitor (in the loose sense).
The payments: Bitcoin.