vfat partition can't be mounted in bbb (ascii)
When trying to mount the vfat boot partition in the ascii images, the codepage is reported as missing so it will not mount the partition.
root@devuan:~# mount /boot/
mount: wrong fs type, bad option, bad superblock on /dev/mmcblk0p1,
missing codepage or helper program, or other error
In some cases useful info is found in syslog - try
dmesg | tail or so.
root@devuan:~# dmesg | tail -n 1
[ 89.079692] FAT-fs (mmcblk0p1): codepage cp437 not found-
What if you avoid the fstab entry and try
mount /dev/mmcblk0p1 /bootinstead?