Filing a DMCA takedown notice on AO3

(Tried to post this question on AO3-specific subreddits but Reddit filters won't let me.)

I orphaned a work a while ago and have been trying to get it reattached to my AO3 account (I have proof of authorship) by contacting Support but, as per the rules, they can't do that.

I'm an EU citizen and this is my first time doing this. I have read the DMCA policy on AO3, but I was wondering if anyone here has already done this and has firsthand experience with what happens after you submit the form, what kind of personally identifying information they will ask for (if any), risk of rejection, how long it takes, etc. And will my request wind up straight on Lumen?