If the SCOTUS decides that citizenship is not needed to vote, it is time to disband this entire Government and start over. I do not trust this SCOTUS to uphold he Constitution anymore. They have demonstrated they will bend to Populist intimidation by Marxists.
Hopefully they will not look to foreign courts or add or change the meaning of words in the law to make their judgment.
It also seems to me that the matter of voter registration is decided by each state unless it violates one of the basic rights of the constitution. I don’t see anything in the constitution that says we take your assertions of citizenship to be true on their face i.e. it is not a test or poll tax.