This is a guide for allowing encryption with Android LineageOS

LineageOS Android Encryption fixing

# DON'T ENCRYPT YOUR PHONE WITH ANY LOCK PATTERN SET (e.g. PIN) BEFORE YOU FOLLOW THIS GUIDE
# Enter terminal (Example TWRP -> Advanced -> Terminal) and type:
df
# df output example:
# Filesystem 1K-blocks Used Available Use% Mounted on
# /dev/block/mmcblk0p12 12324784 546144 60353600 4% /data
# From the above output, we have to remember the mmcblk block and partition numbers (/dev/block/mmcblk0p12).
# Also need to remember 1K-blocks value amount (12324784)

# Now umount /data in TWRP. For this, go to Mount > deselect Data
# Repair filesystem in TWRP terminal:
e2fsck -y -f /dev/block/mmcblk0p12

# Now will shrink partition size by 16K
# For this you'll need to calculate whole partition size from above df output
# For the example above we have 12324784. So 12324784 - 16 we have 12324768
resize2fs /dev/block/mmcblk0p12 12324768K

# Now android LineageOS is ready for encryption
###### Advanced TIPs ######
# To get the size of the partition block you can:
tune2fs -l /dev/block/mmcblk0p12 | grep "Block count"
# Output:
# Block count: 12324784