"${HOME}/Private" does not get unmounted after logout

[René Genz]

On Fedora Workstation 34 after GUI login automount of "${HOME}/Private" works. After log out the folder does not get unmounted. I created a downstream bug report:
https://bugzilla.redhat.com/show_bug.cgi?id=1985799

On Fedora Workstation 36 (branched) the problem exists as well. After logout no user process remains on Fedora 36. I tried to work around the problem by creating a systemd user service that calls `ecryptfs-umount-private` but it would not work. Thank you for any help.

I can reproduce the problem on Ubuntu 20.04 LTS too (preparation is: sudo apt install ecryptfs-utils ; reboot ; ecrypt-setup-private). It seems like part of the following bug report is similar to my problem:
https://bugs.launchpad.net/ecryptfs/+bug/1470030