What about the fact that Bitcoiners still tend to use fiat over Bitcoin, even when they're patronizing a business which accepts Bitcoin? Kinda makes it a tough sell to the next merchant who'd prefer not to go through the effort of setting up a whole new point-of-sale system only for people to not use it.

The number one reason merchants aren't adopting Bitcoin is because Bitcoiners are not demanding it. No one is boycotting business who only accept fiat. Not only are Bitcoiners generally not demanding it, they seem to generally not care at all. So, of course businesses don't care either.

This is what I was initially wanting to do, but getting the money side of it to work out is complicated. Not many businesses want to pay somebody to do this, even if they otherwise wanted to accept Bitcoin. And what they would be willing to pay, even if I was working 8 hours a day, won't make rent happen. At least if we're talking about small to medium sized businesses and merchants. I could be completely wrong about that of course, but that's my read on it. And unlike, for example, coding a new killer app, there's no chance that I am working for cheap now in the hopes of it making bigger money down the line.

Larger businesses might pay more, but then you're getting into long-term support contracts, complying with various standards, integrating with their ERP system, and getting a lot more complicated than "here's BTCPay server configured with what you need" or something along those lines.