Hi,
I hope you are doing well!. I'm Jhun, an independent advisor. Let me assist you with this. Looks like you've already tried several guide, not use if you already tried the following.
Maybe you can try checking the following:
> Your Microsoft Account
Visit: https://account.microsoft.com/devices/recoverykey
I realize you mentioned pending security changes, but it’s worth confirming from a different device or browser just in case.
> Check any paperwork, USB drives, or saved text files you may have created during the original setup.
> If your Surface was ever signed into a work or school account, your IT admin may be able to retrieve the key from their system.
Sometimes the key may have been backed up to a different Microsoft account, if you’ve used more than one, it’s worth checking them too.
If those are not available, best bet is to wait for the security restriction on your account to lift and and once you regain access, be sure to retrieve and save that recovery key in a safe place for future peace of mind.
Best Regards.
Jhun