Trying to understand the "no space left" issue...
Here is the file size:
16.04 Stable (version 23)
ubports 356 Mo compr., 1379 Mo extr.
device 69 Mo compr., 181 Mo extr.
20.04 Devel (version 146)
rootfs 456 Mo compr., 1664 Mo extr.
device 88 Mo compr., 227 Mo extr.
When 16.04 is installed, the extracted size ( 1379+181 = 1560 Mo) corresponds to this partition:
df -h
Filesystem Size Used Avail Use% Mounted on
/dev/loop0 2.0G 1.6G 241M 88% /
What I don't understand is why 20.04 installation is failing; while the extracted size (1664+227 = 1891 Mo) should still be inferior to the 2 Go partition size...
EDIT: I made a trial on my computer. Decompressing both rootfs and device tar.xz on an empty ext4 image file, the used space is 2,041,232 Kb; so more than the phone partition size!
There is not enough free space on the partition to hold the data. The deficit is about 170 MB.