I have bought a used FP3+ in order to have a nearly identical clone of my day-to-day FP3, which is running on /e/ 1.4 and displays a storage size of 64 GB.
FPOS 11 was running on the “clone” device, displaying the storage size accurately with 64 GB. The bootloader menu shows 64 GB, too.
After installing /e/ 1.4 following the recommended procedure, /e/ showed only 32 GB storage size. I encountered the same problem with /e/ 1.11. Something must have happened to the partitions and I need to know how this can be rectified.
I found a few older mentions of an issue like this on other phones in the internet. The recommended solution is a factory reset (which will delete your user data as well as Apps installed by you and their data, be safe with a backup).
This has done the trick. I think it’s important to use the factory reset offered by the respective recovery in order to set the partitions right. I had wiped “data” before using TWRP to no avail, ending up with the dreaded “extracttarfork…255” error.
If I’m not mistaken, TWRP “wiping” the data partition might just result in deleting files, not changing anything regarding the storage format. TWRP has a “Format Data” button to really format the data partition.
Since /e/OS has its own recovery, I think this really should be the preferred way.