Read this if your cache partition isn't big enough to install UbTouch on the nexus 7 2013 (read if you want to risk this on other devices)
Having trouble installing or updating ubtouch? Does the installer say that there's no space left on /cache/recovery?
You're in the right place!
This happened because you used something that resized your table and now you need to resize it to stock. In my case, I executed this script and forgot about it. You'll need to execute the second script in the download-ables of that thread (sysrepartundo.zip).
This exists because when trying to install a big rom with gapps, even the smallest pico package, the system partition doesn't have enough space for the gapps.
Ubports installer or ubuntu-device-flash install the OS in another way, different from the normal .zip flashing that you're used to. It copies the installation files and a script to the cache partition to install it. So if you execute this you'll have your 800 mbs for the system which for ubtouch is more than enough, and 551 mbs for the cache. I never tried this on other devices, but for science you are welcome to.
Also, if the ubports installer fails you, here's a link to download ubuntu-device-flash, which helps you installing it from the command line. Obviously this is to run on a debian based linux os or on the Linux subsystem for windows or in a Virtual Machine.
If i was helpful please write it.
Edit: edited formatting and here's a direct link for ubuntu-device-flash