One of the biggest changes we have seen in 9th edition Warhammer 40k was the introduction of the 'CORE' keyword. The Core keyword has been a saviour when it comes to stopping various units becoming overpowered when character buffs are involved.
The same can be said for the Orks in the new 9th edition 2021 codex.
One of the new buffs that Ork Warbosses now get is the ability to +1 to hit rolls for Melee for units within 6inch. This only applies to <Clan> Core and <Clan> Character units (which is interesting as it means a Warboss with a Power Claw gets -1 to hit and +1 to hit for being within 6inch of his own buff). This is quite an impressive + but not all units are going to benefit from this buff.
So I've put a list together of all CORE units in the new Ork Codex
Hopefully this will help you guys make future choices in adding to your Ork Army before the codex is out for general release.
Note: The Ork Nob with Waaagh banner still has a +1 to hit aura to every Ork unit.