Mystery of Ash's Dad

The Pokémon live play is not canon though, and I don't think the actual writers of the anime helped with it (not sure though). But if Ash's dad is a named character we already know and have seen, Giovanni might actually be his father due to the many similarities in their appearance, and it would also explain why Giovanni kept letting the TRio follow Ash for so long across multiple regions despite them showing no signs of even getting close to catching Pikachu. He lets them follow Ash with the excuse of "capturing Pikachu" so he can make sure his son is safe, either because it's weaker grunts trying to "steal his Pokémon" if the TRio is not aware of Ash's relation to Giovanni or they know and are pretending to be weak so they can help him if things get dangerous, without leaving Team Rocket to become permanent companions, or damaging Team Rocket's reputation by seeming like they are willingly helping people, while Giovanni doesn't directly help Ash or see him often because he doesn't want his son to end up like him. Ash and Giovanni have never met iirc, meaning we haven't seen them react to each other and confirm or deny a possible connection, so it's still somewhat of a possibility.

It's much more likely Ash's dad is just a random trainer trying to become a "Pokémon Master" though. It must feel a bit embarrassing to be saying all that when your ten year old son who you haven't even met in who knows how long and started his journey a few months ago is already World Champion and close friends with multiple legendaries, mythicals, and rare Pokémon, meanwhile you're a grown adult in his 30s or later 20s who isn't very strong or well known (otherwise, Ash's relation to him would have gotten pointed out at some point) and likely isn't friends with even one legendary or mythical.

To be honest I'd rather they never reveal him, makes for wonder.

I agree with @UnovanZorua its probably giovanni it makes sense.

And unlikely.

Ash's dad is most likely a random trainer we haven't seen (and is alive, as proven by that one episode that released before the final 12 episodes), and isn't famous because if he was, someone would have pointed out their relation, with all the people Ash has met across so many years and over 1k episodes.

Of course, if it was Giovanni, he's definitely a secret child, but I honestly doubt Pokémon will ever dare say their protagonist is so closely related to such a villain. It's a good theory, and the way it makes the Team Rocket trio (if they know the relation) look is wholesome, but it'll never be proven (or disproven, probably).