Very Senior Member
Swap file does not need to be on an EXT2, 3 or 4. I have done a swap file on FAT32 USB and it works quite well. I usually use a swap partition and EXT4 partition on a thumb drive created with Gparted. Diversion works quite well with this format.diversion does it, as I recall (I might be wrong, or I might be close), because entware needs ext4. and that's what allows a swap file/folder for routers with low RAM.
It gets inserted into the router and you leave it there...the system drive the router might one day come with ;-)