To be fair it’s 2024 and I’m still doing this, because adding an alternate location to install flatpaks in results in Flatseal not being able to detect those apps or edit those permissions. Just setting the default location as a symlink to where I want to magically fixes everything.
I feel your pain. Flatpack can really ruin partitioning strategies.
It has an installations feature to use any location, as well as users home by default.
Before I realized you could install as user and have it install on your home drive I just symlinked the install directory where i wanted to.
To be fair it’s 2024 and I’m still doing this, because adding an alternate location to install flatpaks in results in Flatseal not being able to detect those apps or edit those permissions. Just setting the default location as a symlink to where I want to magically fixes everything.