Can I link other accounts than British Airways Executive Club to Finnair Plus?

No, at the moment, you can only link your British Airways Executive Club account to your Finnair Plus account. Iberia Plus, AerClub, Vueling Club and Qatar Airways Privilege Club also use Avios, but you cannot currently link these accounts with Finnair Plus.

However, you can link your British Airways Executive Club account to your Qatar Airways Privilege Club or Iberia Plus account if you have those accounts.