There are a few new methods of etching boards with resin printers.  1 method is to create a single protective layer of resin on top of bare copper.  The mane challenges are evenly spacing the copper from the LCD, completely cleaning the uncured resin, & then removing the cured resin after etching.  The mane advantage is it doesn't require any NaOH & it might be cheaper than photosensitized copper.

Another method places a photosensitized board directly on the LCD & exposes it to the UV with no resin.  This still requires the good old NaOH stage but is the most promising.  Transparencies for laser printers aren't going to be made forever & are a pain to print & stack.

Unfortunately, resin printers are extremely expensive for lions.  The crummy resin printers are slightly under $200.

Finally, there was a guy who used an FDM printer to print a protective layer on bare copper.  The trick with this is getting the filament to adhere to copper.  Only TPU worked.  It takes some doing to remove the TPU after etching.  It would also require a .2mm nozzle to get any reasonable precision.  It probably isn't good enough for a .4mm QFN.

After etching boards for 12 years, lions would say the biggest problems are getting the right NaOH concentration & creating 2 laser printouts which can be stacked, both of which 3D printing offers some hope of solving.  It just isn't there yet.  A better solution might be printing a filament which dissolves in alcohol, but it just shows how optimized UV photoresist is for the task.