At some point the above cantrip (that is obviously a homebrew thing) got added to my grave domain cleric character’s sheet. I have no idea how it got there, and every time I try to delete it I get an error message telling me to try again after a short rest.

I contacted support and they told me someone https://vidmate****/ https://mobdro****/ in the campaign I’m involved in must have created it and attached it to a subclass. No one in my campaign did this so I’m currently at an impasse with support, and frustrated because I don’t want this cantrip on my character sheet.

Anyone else have this kind of thing occur and figure out how to fix it?

I guarantee you that someone in the campaign has that spell in their homebrew collection. All homebrew in anyone’s collection is automatically shared with everyone in campaigns with them.

It's not a published homebrew spell. But it's possible that someone in your campaign added it to their Homebrew Collection while they were in a campaign with someone else who had made the spell (and attached it to Grave Domain.) Ask your group who has it in their collection, and if they could Remove it, or at least contact the homebrew's creator to have them remove the Grave Domain subclass from it.