Remove Chrome Policy. Error: Domain (com.google.Chrome) not found
MDM management is tricky to remove since many times, the business will force several mechanisms to prevent easy removal.

Make a full backup, seriously - Time Machine to a local disk is my recommendation in addition to however you typically back up.
Look in system preferences for a Profiles pane. It will not be visible if you are not MDM managed.
Contact the old business - ask them to send clear written instructions on their removal process. Get it in writing. Prepare an invoice if they say it needs time or to be sent to them (many won’t divulge how to remove which isn’t fair if they’re not paying you to undo what they did to you)
Proceed and if all goes wrong, you can always erase the Mac and restore from backup.

You will need to explain in much more detail what Apple signed tool you are using, but first thing is to be sure MDM isn’t foiling your attempts to manage chrome.