I’ve had the same problem and the /boot partition went full, see No space left on device while update-initramfs
I had to remove the 5.13 kernel (see there) and now I only have the 5.16 one:
purism@pureos:~$ ls -l /boot
total 251153
-rw-r--r-- 1 root root 2328 Jan 23 07:12 boot.scr
-rw-r--r-- 1 root root 2328 Jan 23 02:18 boot.scr.bak
-rw-r--r-- 1 root root 187855 Jan 17 11:33 config-5.16.0-1-librem5
lrwxrwxrwx 1 root root 53 Jan 23 07:12 dtb -> dtbs/5.16.0-1-librem5/freescale/imx8mq-librem5-r4.dtb
lrwxrwxrwx 1 root root 53 Jan 23 07:12 dtb-5.16.0-1-librem5 -> dtbs/5.16.0-1-librem5/freescale/imx8mq-librem5-r4.dtb
drwxr-xr-x 5 root root 1024 Jan 23 02:17 dtbs
drwxr-xr-x 2 root root 1024 Jul 13 2021 grub
-rw-r--r-- 1 root root 64325755 Jan 23 07:12 initrd.img
-rw-r--r-- 1 root root 64325755 Jan 23 07:12 initrd.img-5.16.0-1-librem5
-rw-r--r-- 1 root root 64325426 Jan 23 02:18 initrd.img.bak
drwx------ 2 root root 12288 Sep 11 07:31 lost+found
-rw-r--r-- 1 root root 4941866 Jan 17 11:33 System.map-5.16.0-1-librem5
-rw-r--r-- 1 root root 24610824 Jan 23 07:12 vmlinuz
-rw-r--r-- 1 root root 8815340 Jan 17 11:33 vmlinuz-5.16.0-1-librem5
-rw-r--r-- 1 root root 24610824 Jan 23 02:18 vmlinuz.bak
purism@pureos:~$ df -kh /boot
Filesystem Size Used Avail Use% Mounted on
/dev/mmcblk0p1 451M 248M 180M 59% /boot