I'm looking for recommendations for a low-end laser printer. I don't
need networking and I'd like to keep things as simple as possible, so
I'm probably looking for just a usb printer which works with cups.  I'd
very much prefer one which doesn't require proprietary firmware to be
loaded or anything to be installed outside of portage.  I'd Duplex
printing would be a plus, but not necessary.

For reference, if the Brother HL-L2300D works easily with cups, it
would suit me fine.  (But I don't have any preference of manufacturer
-- I just happen to have the Brother URL handy as I'm typing this.)
<https://www.brother-usa.com/products/HLL2300D>