New Windows 11 Install Issues

Hello,
I recently purchased a new (to me) HP 840 G9 through ebay. When I went to do a fresh install of Windows 11 Pro I was prompted to login to a school/business. I assume this is because the computer is still registered in Autopilot, Azure, or something. I contacted the seller, on ebay, and they had no idea what I was talking about (or at least claimed ignorance).

Anyway, I was able to bypass this by reinstalling Windows 11 Pro and doing the ol' OOBE\BYPASSNRO trick when the install process asked me to connect to the internet. So far, everything is working like a brand new computer, i.e., I was not prompted to login to any company/school and I was able to rename the computer and link it to my MS Account. Additionally, I flashed the BIOS to the latest version, replaced the SSD and confirmed the license is an OEM license.

However I have some questions:

• Since this computer is still registered somewhere will this cause any issues in the future?
  • At this juncture, can the previous company/school, who owned this computer, still access it, even though a fresh install of Windows 11 Pro was performed without logging in with the company/school's credentials?
  • Is there any way to deregister this computer if I don't know what company/school owned it before me?
  • Are there any other issues that may arise that I should be aware of?