Ok this is what i did to fix the problem on Bazzite thanks to this thread : Can't get past Grub and Dracut shells after ostree upgrade - #7 by gucci-on-fleek - Fedora Discussion
I’ve used a Linux live usb (Fedora core OS)
Booted from the usb.
On my system :
nvme0n1p6 = home, var, root,
nvme0n1p5 = boot partition
nvme0n1p1 = EFI
mount /dev/nvme0n1p6 /mnt/
mount /dev/nvme0n1p5 /mnt/root/boot/
mount /dev/nvme0n1p1 /mnt/root/boot/efi
mount --bind /dev /mnt/root/dev
mount --bind /proc /mnt/root/proc
mount --bind /sys /mnt/root/sys
deploy="/ostree/boot.1/default/c638c18f507947f25d5a11f5a8c64960684f04c9d0c059d5ed02a679983937b7/0"
mkdir /mnt/root/usr && mount --bind $deploy/usr /mnt/root/usr
mkdir /mnt/root/etc && mount --bind $deploy/etc /mnt/root/etc
mkdir /mnt/root/bin && mount --bind $deploy/bin /mnt/root/bin
mkdir /mnt/root/sbin && mount --bind $deploy/sbin /mnt/root/sbin
mkdir /mnt/root/lib && mount --bind $deploy/lib /mnt/root/lib
mkdir /mnt/root/lib64 && mount --bind $deploy/lib64 /mnt/root/lib64
chroot /root/
rm /boot/bootupd-state.json
/usr/libexec/bootupd install --auto --with-static-configs --write-uuid /
exit