I'm not really against it if there is a demand and people want to buy/sell/trade here. If buy/sell/trade gets too much we could restrict it to a sticky thread.
It might be easier for people to find buyers/sellers on the framework forum category that @narc0tic_bird@lemm.ee pointed out though.
I have run Fedora and NixOS on my framework. Both run well, Fedora is equal/close equal to Ubuntu in ease of use.