Choose an HP all-in-one model and follow Chris' instructions to check whether
Trisquel will perfectly support it:
https://trisquel.info/fr/forum/hp-laserjet-printer-p1005-printer-not-working-trisquel-60#comment-77026
If not, choose another one.
You can support ThinkPenguin (Chris is its CEO) and Trisquel (by using the
following link, 25% of the benefits on your purchase are donated to the
project), by buying from http://libre.thinkpenguin.com (all the hardware that
is proposed works with Trisquel: no need to check anything).