Where did National Dex Doubles Ubers go on Showdown?

Hey all, quick question—

I’m trying to test a team for a league I’m in, but the only format my team is allowed is National Dex Doubles Ubers, and I can’t seem to find it anywhere on the Pokémon Showdown battle list to test it.

I thought it used to be there (or at least selectable), but now I only see regular NatDex formats—nothing that combines both with Ubers rules.

Did the format get removed, or is it just not always available? Is there a way to still play it outside of direct challenges?

Appreciate any help!