How to fix import errors in the Mail application?

AppointmentChallenged wrote:

It' been some moths since any responses. My wife's MacBook Pro got this message:

"The Import Failed.

An error occurred during the import. Make sure you have available space in your home folder and try again."

I tried fixes that worked for others. No good.

Has anyone got a new (preferable easy) fix for this?

Thank you!

ref:

Import or export mailboxes in Mail on Mac - Apple Support

Import emails from another account into iCloud Mail

See if there is anything here...

migrating old macOS MAIL to new M1/M2 machine ISSUES— see VikingOSX

Can't Upgrade Mail from Catalina to Ventu… - Apple Community

Some have found—Restarting in Safe mode and try again the import:

Start up your Mac in safe mode – Apple Support