hi all. Reading the doc about installation of KaOS with a btrfs on ssd, the /etc/fstab in example put the option discard when mount /. i have read, in other docs, discard is obsolete for the modern ssd. which is truth? I have a new ssd, i need of this option in fstab? only for btrsf? and with xfs?
thanks!

I don't use the discard mount option for any filesystem. btrfs has the option ssd for SSDs (which is btw autodetected and automatically enabled).

Not because out of fear for performance issues, but because I don't think it's need. All modern Linux Filesystems accommodate for Solid Storage Devices, some better than others. And the Firmware of SSDs does what it wants anyway.

Currently the kernel folks are working on async IO, one of the fruits is for example is "async discard" for btrfs with linux 5.6. But "online discard" how we expect it to be will only happen after all filesystems have accomodated for async IO and the FIrmware of SSDs plays ball with it. Until then, a systemd-service with fstrim is all you need.