you have to run apt --autoremove or something. If you don't, debian/ubuntu updates will get slower and slower as it has to rebuild some index for every kernel available on the system. Removing all of the kernels you're no longer using fixes the storage space issue, but i am unsure if apt will freak out if it can't find a kernel it thinks is installed. apt --autoremove will uninstall and de-index all of the old kernels for sure, though.
Yes, I even added --purge to gain an extra notch in the process, but it all fell 37MB short in space. The next alternative is to shrink /home and expand /boot, but (2) I would have to do it via an USB booted Ubuntu, but (3) my SSD has LUKS, so I don't know how gparted would deal with it. I feel the risk of losing some data... I do have backups, but (4) not the time nor the patience to go through all this.
