At this point, like with many things, you'll have to go model by model and not trust a whole company to do something right. I have several of the Netgear R6220 router running OpenWrt, but Netgear as a whole tends to not have OpenWrt support, so I would never blindly recommend someone buy Netgear. Instead I'd say to look at the Table of Hardware on OpenWrt's site. That being said, a list of "good" printers somewhere would be fantastic. I have an old HP monochrome laser printer (sorry to be part of the problem, don't have the model handy, may edit it in later) I got at a thrift store, it happily accepted some very cheap toner I got from eBay. I understand everyone has hated HP printers for years, though I think it's mostly the inkjet models.
In a recent Louis Rossmann video that covered this Brother printer issue, there were some suggestions in the comments, Minolta if I remember correctly.
So ... not HP, not Brother ... anyone left that sells reasonable printers with honest firmware?