Looking through the actual DMCA takedown request, it seems that the "MorpheApp" project were the ones to file the takedown request. In the request, they claim that they made a hard fork of ReVanced due to apparent harassment from the leader of the project (though their exact role is redacted in the takedown request, further research seems to support that this individual would in fact be the ReVanced leader). They also go on to claim that ReVanced stole patches from them.

In ReVanced's where-is-revanced-patches repo they claim that "it has no legal basis", without making any attempt to address the individual complaints in the takedown request.

Also, while attempting to find what "harassment" the MorpheApp member faced, I found a new repository called "De-Vanced" which appears to port ReVanced patches to Morphe. And to make it even more confusing, this repository was apparently created because ReVanced claimed forks were unofficial, despite being a fork themselves. Of course, ReVanced and another project that was forked from Vanced have the same amount of legitimacy or "officialness", but they are free to label ReVanced forks whatever they deem. Unofficial might be harsh language though, since this is open source.

So the leader of the ReVanced project (oSum) has posted on Reddit showing his side to the story:

https://redlib.catsarch.com/r/Piracy/comments/1q26tvw/comment/nxblagk/
https://drive.google.com/drive/folders/1Q3vDC-vleraH2iZPS0c7JrdQeQr98O5k
https://redlib.catsarch.com/r/revancedapp/comments/1q2ar6e/context_provided_from_revanced_regarding_recent/

This all started because the rest of the ReVanced project wasn't very happy with the design of some proposed fix, and the developer who wrote the fix PR started MorpheApp.
Apparently, the developers of MorpheApp squashed every ReVanced commit and added additional clauses to GPLv3. And according to oSum, he was the harassed party. Amazing!

Pretty funny stuff