Slow writes with Btrfs + LUKS + NVME SSD

[Tobiwan]

Seems that I fixed the issue by allowing TRIM on Luks

(by adding :allow-discards to cryptdevice=UUID=205e4e87-163d-...:luks-... in GRUB_CMDLINE_LINUX_DEFAULT= in /etc/default/grub + sudo update-grub)