they do some squirrely stuff to try to get you to buy a new toner cartridge early

My brother is newer than yours (the cheapest one I could get that prints on both sides of the paper), and has a setting to toggle how it behaves in low toner mode.

The default is to pause printing until you replace the toner - honestly that’s not entirely wrong. Having the printer run out of toner half way through an important print job could be a disaster.

The alternative mode is to just show a “low toner” warning badge whenever you print a document. That’s what I use, but I also check if it printed properly before closing the document which a lot of people don’t do.