I'm aware Pokèmon that are GMAXED/DYNAMAXED aren't alternative forms like megas in past games. However, Quite a few online had managed to get Dynamaxed mons in boxes and their main party of 6. It raises my curiosity on how that's possible? Is it something with within PkHex itself? Not sure.
I know this wouldn't be possible In the case of Eturnamax Eturnatus only due to the fact that it's impossible to have his form in boxes permanently. But this is only because of him not being coded to do so (correct me if I'm wrong).
If there is infact a way to get Dynamaxed or Gigantamaxed Pokèmon in boxes or your main party itself, I'd really like to know. It'd be interesting to have it as a sort of collective mon.
