fstrim doesn't trim my /home separate partition

[Francisco T.]

My system is Kubuntu 20.04

I have 3 partitions in my nvme:
NAME MAJ:MIN RM SIZE RO TYPE MOUNTPOINT
nvme0n1 259:0 0 465,8G 0 disk
├─nvme0n1p1 259:1 0 251M 0 part /boot/efi
├─nvme0n1p2 259:2 0 53,7G 0 part /
├─nvme0n1p4 259:3 0 7,6G 0 part [SWAP]
└─nvme0n1p5 259:4 0 357G 0 part /home

I have activated fstrim.service and fstrim.timer:
sudo systemctl list-timers
...
Mon 2021-06-21 00:00:00 CEST 3 days left Mon 2021-06-14 00:00:03 CEST 3 days ago fstrim.timer fstrim.service

But home partition is not trimmed:
...
jun 14 00:00:10 moon fstrim[5137]: /: 29,1 GiB (31264600064 bytes) trimmed on /dev/nvme0n1p2
jun 14 00:00:10 moon fstrim[5137]: /boot/efi: 239,1 MiB (250755584 bytes) trimmed on /dev/nvme0n1p1
jun 14 00:00:10 moon systemd[1]: fstrim.service: Succeeded.
...

The fstrim.service is Protected for home:
sudo systemctl cat fstrim.service
# /lib/systemd/system/fstrim.service
[Unit]
Description=Discard unused blocks on filesystems from /etc/fstab
Documentation=man:fstrim(8)
ConditionVirtualization=!container

[Service]
Type=oneshot
ExecStart=/sbin/fstrim --fstab --verbose --quiet
ProtectSystem=strict
ProtectHome=yes
PrivateDevices=no
PrivateNetwork=yes
PrivateUsers=no
ProtectKernelTunables=yes
ProtectKernelModules=yes
ProtectControlGroups=yes
MemoryDenyWriteExecute=yes
SystemCallFilter=@default @file-system @basic-io @system-service

I think the problem is:
https://github.com/karelzak/util-linux/commit/61b384b36105fe682ddf16b9379f446d935603bc

[Launchpad Janitor (janitor)]

Status changed to 'Confirmed' because the bug affects multiple users.

[Steve Dodd (anarchetic)]

This is due to "ProtectHome=yes" in the .service file; the workaround is to add:

[Service]
ProtectHome=no

In e.g. /etc/systemd/system/fstrim.service.d/allow-home.conf