Missing pictures and albums after moving library to new mac

Is the transferred library in your Pictures folder or on an external volume?

By " reindexed photos with no change. " do you mean, you have been running the library repair tool?

The copied Photos Library may still have permissions and file ownership problems. Try to repair these manually.

• Quit Photos, if it is running.
• Select the Photos Library in the Finder, then ctrl-click it and use the command Show Package Contents".
• Select the "database" folder inside, then use the key combination ⌘i to open the Info. Open the permissions brick at the bottom of the info, unlock it, and set the permissions to give you read/write access. Now click the gears icon to use the command "Apply to enclosed items.
• Do this for all files and folders in the package.

Then try again to open Photos.

If it still does not work, try again to repair the library with the library repair tool: https://support.apple.com/en-gb/guide/photos/pht6be18f93/mac

Use the method on any folder in your Photos Library to correct the permissions.

The conversion to a Catalina Library does not yet seem to have been completed.

Perhaps after the permissions repair Photos will be able to finish the conversion.