Unable to save changes

I’ve just upgraded from an old Mac running OS10.6 to a new iMac running OS11.2.3. I’ve installed Libre Office V7.0.5.2, but everything now opens as read only and I can’t save any changes to documents I created on the old Mac.

When I try to save, I get the error message “Write Error. The file could not be written”.

If I try Save As, with a different name, the error message is “Object not accessible. The object cannot be accessed due to insufficient user rights”.

If I try Save a Copy, the error message reads “General error. General input/output error”.

I’m the admin on the Mac, I’ve given Libre Office full disk access, and I’m out of ideas.

Does anyone know what’s going on, please?

Thanks
Matt

Maybe a rights issue? See: permission - macOS and File Owner information - Ask Different

And: How to Change File Ownership in Mac OS X