When the SD card is formatted as ext4 it will not mount (missing driver?):
[ 8.770000] scsi 0:0:0:0: Direct-Access Generic STORAGE DEVICE 0933 PQ: 0 ANSI: 6
[ 8.940000] sd 0:0:0:0: [sda] 246016 512-byte logical blocks: (125 MB/120 MiB)
[ 8.960000] sd 0:0:0:0: [sda] Write Protect is off
[ 8.970000] sd 0:0:0:0: [sda] Mode Sense: 21 00 00 00
[ 8.980000] sd 0:0:0:0: [sda] Write cache: disabled, read cache: enabled, doesn't support DPO or FUA
[ 9.000000] sda: sda1 sda2
[ 9.000000] sd 0:0:0:0: [sda] Attached SCSI removable disk
[ 9.340000] procd: - init -
[ 12.700000] EXT4-fs (sda1): Cannot load crc32c driver.
[ 12.750000] EXT4-fs (sda1): Cannot load crc32c driver.
[ 12.770000] EXT4-fs (sda1): Cannot load crc32c driver.
[ 13.270000] Adding 124k swap on /dev/sdcard/sd2. Priority:-1 extents:1 across:124k
If sd1 is formatted as ext2 the sdcard is mounted (without journaling however.)
In addition, formatting from the USB menu in webUI does not create a filesystem partition. Only a swap partition is created.