Time Machine not dismounting

I can not eject my external Time Machine drive. I’ve read that this is an old problem, but haven’t seen a workaround anywhere, other than shutting down the computer.

I do want Time Machine to be my backup in case I get a exposed to a virus/ransom..

For this reason I do not want my drive attached to the network other than when I backup. Hence I would like to be able to freely mount and unmount.

Has anyone found a way? Or is Apple trying to sort this out?