Several of the Mac apps that I consume seem to use Paddle for licensing, and this seems to solve your issue in regards to the machines likely to run this.
I have absolutely 0 experience with it but from their website it seems like they handle "everything", if that's what's usually understood by being a Merchant of Record.
An electron app might be a good fit.
This course is from the Laravel community. I've met Marcel at Laracon, his products are worth the price of admission. He's putting out some amazing stuff.
https://desktopappswithelectron.com/
This course teaches how to add licensing to your Electron apps to distribute and sell them easily.
His course covers licensing so you can charge for your app.
Good luck, sounds interesting.
If there's no service that's offered on an on going basis (ie servers running, storage, etc)
I'd say the easiest option is just open source it and run donations / pay-for-help.
You don't want to run a business, yet you're asking for help on running a business.
There's many more factors that take up your time as well, such as marketing, server costs, licence costs in the case of apple, etc.
If you want to run a business then you've got a real good lede, but if you don't want to run a business I'd say; just don't, and put up a tip jar / "let me help you" price.