I just checked, config option --with-x-toolkit=motif still works with 30.1
In a way I would be surprised if motif is removed, I think FSF still wants to support proprietary UN*X and for that you really need to support motif.
FWIW, lucid and athena is still allowed too.
I checked because a person in LQ/Slackware always recompiles Emacs with motif support. He/She would have complained in the group if motif was removed :)
I think that Motif support has been removed from latest Emacs, it is still there in v29.