I read about your home partition troubles. I ran in to that recently as well. Similarly I thought I would quickly try stable diffusion. Ended up not being as quick as I had hoped. I had to boot gparted and resize root and home. I had done that before at some point; but I keep forgetting how to do things. I was unsure if it is safe to do that without the latest version of gparted, so to be safe I redownloaded it and updated my system as well. Of course I have some old Nvidia hardware that tend to make my upgrades painful, so that took not so little time too.
I'm not really sure why having a separate home partition is even beneficial to begin with. Next time I make an install, I might just go without that.