Per https://together.jolla.com/question/...vm-volume-size all these tedious workarounds become unnecessary.

I cannot comprehend, why Jolla still sticks to 2500 MB root volume size per default, despite numerous bug reports since 2015 (when they started using LVM), a pull request in their Git etc.

Well, the logic "this only affects power users and they shall be able to help themselves" is dreaded, but has some appeal:
So help yourself (because Jolla won't)!