Yes, TRIM is supported. However, it is best not to use the discard mount option in /etc/fstab and to use systemd's fstrim.timer instead.
discard attempts a TRIM on every write, which not only impedes performance but may also fail if the number of blocks to be discarded is too small. fstrim.timer on the other hand runs once a week ─ usually Sunday at midnight, or upon the next boot if the machine was not powered up around that time.
In order to enable fstrim.timer, all you need to do is…
sudo systemctl enable --now fstrim.timer
… and, as I said, remove discard from the mount options for your filesystems in /etc/fstab.
I’ve recently done a new install, I’ve realized that the discard option wasn’t by default anymore in my fstab file.
In addition, I start fstrim.timer with:
You can cover both of those commands with the single command…
sudo systemctl enable --now fstrim.timer
Yes, the timer runs every day, but the service is run only once a week. The service is what does the trimming. The timer is only there so as to determine when the service must be run.