Since last Windows Update "task host window is stopping background tasks windows 10" on 4 machines

Yep, I have exactly the same issue.

For me it is since the two updates - KB5016616 and KB5012170.

So I don't know if this narrows the culprits down from the 3 updates you mention.

Hopefully this will be sorted soon. It's irritating.

Yep, exactly the same for me too. No matter how long you wait, it will never shutdown. You can't fix it by using sfc /scannow or DISM commands or by uninstalling the offending updates. Be careful if you choose the "Ignore and shutdown anyway" option because it may corrupt your login profile. I had to do a system restore to get my login profile back! There should be an option to defer updates for several months to give MS time to verify them! Hopefully somebody will find a fix soon!

Since forcing the shut down is the only way to turn off the PC, how can I be careful about it?

That is what I do. Choose shutdown anyway

Since forcing the shut down is the only way to turn off the PC, how can I be careful about it?

I suggest not stabbing the "Shutdown Anyway" in haste as I did. I now count to 10 before taking out my frustration, just to give it plenty of time to finish....

Did you try the approach I took as I have not had the problem since.

You said you would try and post back and it would be good to know if it worked for someone else