What do you suggest for a good used Mac for being able to release Godot games on?

A used mac mini should probably do. Should be possible to find something starting from ~250. The more recent the better of course but for just simple things like exporting might not need anything too new. Mind, that it's been about a decade now since I last had a mac tho.

You will want one of the M1 Macs if you want something decent. You can get older Macs for cheap (I'd even send you my old MBP, if you want) but they are slower for Godot, particularly in 3D. For 2D, even the old Intel Macs will be okay but I would say not worth the money. For an old used one (but not too old) you are probably looking at $400 or $500. But for $800 you can get the 2020 model. This is the one I have, and I can vouch for the seller (this is the exact listing).

https://www.ebay.com/itm/363224918564?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2060353.m2749.l2649

Note, it says open box, and the box was open, but my laptop was brand new. Not sure if they made a mistake or what, or if I just got lucky. But it's a trustworthy seller. Just note, even on that one, the 3D is not spectacular. My demos were running at 30 fps. So yes, watchable, but not great. For low poly simple 3D it's fine and it's really fast for 2D. Or, let me know if you want my old MBP. It's from 2017, I believe, so not the fastest model but it should run Godot.

Okay, let me dig it out the closet and make sure it still works. I think Macs last a long time but I probably haven't turned it on in 2 years and I'll never use it again.

I found the charger. Had to dig though every box, and (like always) it was in the box all the way in the back on the bottom. It's charging now. Later tonight I will make sure it still works and test Godot.

because of the mac license, and windows using switches, I think I might release my next project in only linux.

You know, I was initially thinking the same thing, but I wanted to be inclusive and it's not an "us versus them" battle. Many people use Windows or macOS because they are not technically minded to use Linux (or don't think they are, because of a perceived or real notion that Linux is for programmers or is too hard to use). And it would be unfair to not let them play the game just because they are not as smart on the computer or that they have been tricked by Microsoft or Apple. That is not really their fault.

To give you an idea of the percentages, on Ella (on Itch). I got 3x as many downloads from Windows as I did on Linux. And I got 3x as many downloads on Linux as I did on Mac. So Mac is not as significant, but still some action. And I was surprised by the Linux numbers, considering the overall market share, but I think this is because no one games on Mac, and also that Linux users are more likely to play weird indie games and tech demos (while Windows users may be more interested in AAA games).

So the Macbook works, however it is older than I thought. The 2012 model. I am updating it now and I will check that Godot works. It does seem a little slow, but it's probably good enough if you are just using it for exporting and testing and not as your main development machine.

So I spent the day testing it. The computer is definitely slow, but it works well enough. Godot basically runs at full speed and 2D is no problem, even some simple 3D is okay. Stuff in the OS can be slow, though, so like clicking to open a folder can take like 5 seconds. But it works.

I even tried some low poly 3D games and they were running at 60 fps (though at SD resolution). I did try my demos and they crashed, cause the laptop only has 4GB of RAM and that is not enough. But it should be fine for you. Send me a PM with your new address. Cheers.

Oh sorry, I got so caught up with this book project, I forgot to ship the laptop. I'll send it tomorrow.