Mac Studio freezes at login after changing user account name

Hi y'all. Hope I can get some help here.

So, I'm a video editor and was laid off from my job of 10 years. I used a personal computer for a long time for my work, and then eventually got a work computer and migrated my personal computer to my work computer. Now, years later, I've been laid off. They want their 2025 M4 Max Mac Studio back.

I bought my own 2026 M5 Max Mac Studio and I backed everything up from my work computer via Time Machine. They had some admin stuff on the work computer but when I set up my new Mac Studio via Time Machine and didn't select the admin user accounts, all those softwares seemed to be left behind. (Also, the old Mac Studio is on Sequoia. I don't think I can update it. My new Mac Studio is on Golden Gate)

Everything seemed to be working great and I had full permissions after setting it up. One problem is, I wanted to change my user account name and home folder because I didn't want it to have the company who just laid me off's name on it lol

I tried something via ChatGPT and Terminal initially. Made a new admin user account, etc, etc. Restarted. Tried logging in. Spinning wheel. Force restarted the Mac again, tried logging into the other user account. Also frozen. Eventually, had to wipe the entire Mac and start over.

Then followed these instructions from Apple which again involved making a new admin user account. Restarted. Tried logging in. No spinning wheel this time but it froze at login, so same result. Other admin account frozen at login too. Had to wipe the Mac and start over.

I felt like I maybe mixed up a step the second time I tried it, so I did it again. Third time around, I followed Apple's instructions PERFECTLY. Felt extremely confident I did everything correctly. I restarted. Tried logging in. Same thing as last time. No spinning wheel but froze at login for the account I changed and the admin account I set up.

One other thing that maybe matters or maybe doesn't: my user ID was showing up as 504 it seemed like, even if I only transferred 2 user accounts via Time Machine. (I had a "personal" MacOS user account I never used and then the user account I actually used for work. I transferred both during 2/3 of my attempts setting up my Mac Studio)

Any idea what I might be doing wrong? Any alternatives to this? Like, I'm almost tempted to try to somehow rebuild everything manually with a fresh new account but since I'm a video editor, I'm concerned about some plug-ins and whatnot that could be deeply buried in Application Support folders and whatnot.

Sorry for the long post, but wanted to give as much context as possible.

Appreciate any help I could get!