I just upgraded to Monterey and my email flags are all gone and cannot search after 2018! what gives?

Option-Click the header word SUBJECT and select Flags from the drop down menu to restore flags to the column view.

Had the same problem.

Can you see the flag at the top left under "all mailboxes"?

R click it to see the dropdown, click to turn on the ✔️

Now you should be able to flag (colors and all) msgs like before.

In Apple mail what setup from the View Menu is being used ?

If using the " Use Column Layout " refer to first picture

Then in Subject " Header " refer to second picture

Right Click the word Subject and a sub Menu should appear and Enable Flags

Same problem here and this didn't help me at all. I'm in Column layout.

Monterey MacMail seems to do something different every time I open it