Thanks in advance to those who will take the time to answer me.
A few days ago I decided to make the switch from GRUB to systemd-boot, with the aim of simplifying and speeding up the boot a bit.
I followed this guide and it worked perfectly: https://kowalski7cc.xyz/blog/systemd-boot-fedora-32
The problem occurs when I decide to restore a snapshot of a few days ago, with Timeshift , where it always worked when I had installed GRUB, on reboot I have a failure on boot, solved by restoring the previous snapshot from live again .
I found that with systemd-boot the boot configurations and kernel images are on the efi partition at mount “/efi”, so obviously excluded from snapshots (and I suspect this is the cause).
 While installing Fedora, I rename the subvolumes “root” to “@” and “home” to “@home” to make Timeshift work, I add additional subvolumes of: