I found a HP b&w laser printer at thrift for like 10 bucks, got some knock off toner from Amazon and it works perfectly. It's never been online since I've owned it so if it is doing anything spooky, it won't be able to send it anywhere and it shouldn't be any info that traces back to my anyways.
But I totally get your frustration with printers, even without all the DRM and tracking BS, printers are consistently the worst piece of modern technology to deal with. A teletype or your 3d printer autopen idea would definitely give any letters you write more character so idk maybe it's worth the effort to get something like that working?