Thanks for the reply, but I found my own solution. Once I clicked on the .deb I just saw a big highlighted button saying "Install Zoom" and clicked it, and it installed zoom again but... I thought it installed it from the .deb, no... Instead it just found it in the store and installed it from flathub...sigh
You're supposed to select the less shiny, less highlighted "Run anyway" button.
Would be nice to make this a bit more obvious, I had this happen before.
Unrelated: how do I find a UI alternative to the package manager, or something that just shows me .deb packages, and not flatpaks or snaps.. or anything like that, several times already I installed the app from "Software" and the app just wouldn't work correctly and it was always because it's a flatpak...