I tried the following
sudo cryptsetup luksChangekey /dev/nvme0n1p3 < new passphrase >
It then asks for the Sudo password, then asks for the old passphrase, but then it prints this error message
Failed to open key file.
what went wrong ?
Edit: turns out using GNOME Disks is way more straightforward… 😅, thank you all
Try clicking on the encrypted partition to get the passphrase option.
https://askubuntu.com/questions/95137/how-to-change-luks-passphrase