Stuck with "optimizing your mac" window when migrating macos high sierra to MacBook Air M2 with Monterey..

Q - " I have the new MacBook Air M2.. My old MacBook Pro is 2011 version so the latest macos it can work with is High Sierra (10.13.6).. There is approx 900G of data and systme on 1T hard drive to migrate... Migrating the whole drive,"

A - As an earlier posting suggested, " If you are willing to restore your new Mac to factory fresh configuration " Credit to steve626

I would suggest a considering a different take on the Migrate process.

Below is IMHO

If the new computer is going to be the Apple Silicon M1 / M2 Equipped Computer - would suggest Only Migrating the User Account and nothing more.

Some have had success and others have been left with a mess when Migrating everything.

1 - Apple Silicon with Monterey macOS 12 Only Support everything 64 bit and there is no workaround.

2 - Issues that may exist on the older computer will be migrated to the New Computer. This would badly pollute the new Original and Pristine installation of the new OS.

3 -  Applications, extensions and Software Drivers may or may not even work on the new computer.

4 - IMHO - it would be best to only install new application etc Directly from the Developer or the Apple Apps Store.

5 - Due Diligence on New Applications and make sure they are Monterey compatible and factor in the ARMs CPU of the Apple Silicon Computer  

I get a message the the computer is "Optimizing Your Mac" which does not go away..

No, it never will. It is not a status indicator, just a message indicating you might get some slow or klunky behavior for a while.

I can’t explain why Apple Support doesn’t know that.

I've never had that message not go away after a period of time varying from a few hours to a few days, Why it varies I could not say. Presumably different amounts of optimization to do depending on system contents and system versions.

If you are willing to restore your new Mac to factory fresh configuration and redo the migration from your backup, if you just migrate user accounts and files only, no settings and no "other" and no applications, you may find that the "optimizing" process is faster.

"Optimizing" includes creating a Spotlight index, updating some Photos Library items, and other things. The more files and the larger your Photos Library, the longer this will take. Also, if your Mail has lots of messages, that will also take a long time.

If you somehow interrupt the process, it will have to start all over, so best to let it complete. You can use the Mac in the meantime.