Such as Tradera in Sweden where I live (they don't try to make me install the app on Tradera at least).

If I'm buying random funkis furniture or computer bits and bobs I can probably use Tradera, and if I want fancy furniture or jewlery or something then there are coalitions of auction houses like Auctionet out there - but as soon as something gets even mildly obscure then there's nothing that has the reach and coverage of eBay.

Starting a new online auction site sounds like a terrific way to throw money away.