I am a collector of certain goods and I ocassionally check 2nd hand sites in countries across Europe.
I know Netherlands has Marktplaats
A lot of countries are starting to use Vinted now within Europe
Germany has Kleinanzeigen
Scandinavian countries have Tradera
Finland has Tori
Spain/Portugal/Italy = Wallapop
France has leboncoin
Belgium/ france has 2de hands.
Am I missing some?