It's not visible there, probably because I obliterated the Dropbox.app file.

Currently rm -rf'ing the kext after kextunloading it and seeing the kextcache rebuilding.

Why should I trust a company that gets its customer database leaked with a kext that they install via shady deceiving permission dialogs?!

Uninstalled. Good riddance.

I tried this, but looks like Dropbox shenanigans are able to silently turn it back on.

No, that works only until your next reboot. DB has installed an agent that resets that setting in TCC.db a few seconds after you log in next.