Comment 12 for bug 1770093

Ack, good point thanks - I updated the patch to:

@@ -87,7 +87,9 @@
     fi
     # base-passwd defines gid 46 as group plugdev
     if [ "$method" != efi ]; then
- options="$options,umask=007,gid=46"
+ if ! ([ "$mountpoint" = "/boot/firmware" ] && grep -sq "Raspberry Pi" /proc/device-tree/model); then
+ options="$options,umask=007,gid=46"
+ fi
     fi
     echo "$path" "$mountpoint" vfat $options 0 1
    fi

@adamsmith can you test with this patch to make sure it fixes the install problem? I have builds of partman-basicfilesystems in this ppa:
https://launchpad.net/~ddstreet/+archive/ubuntu/lp1770093