https://www.bleachbit.org/
I mostly wanted to use it to super-clean my Firefox browser. I somehow feel fresher after it vacuumed my database!

I converted to a standard xzm, not the zstd one - I didn't test that far. Running the regular-user version worked fine, I didn't need to run as super-user. However when I tried to run like that, nothing happened. I did the college try of logging out and logging back in, but just the normal user version worked fine. I'm good.
Update: (launching as root in a terminal was easy enough if one wants to do that)
Just saying that I didn't download ALL the various different versions from bleachbit, test all the standard xzm vs zstd xzm and so forth...
I dig it.