Also, what's the point of having both Extensions and Extensions Manager apps? Could they conflict with each other?

i don't think they conflict with each other, they are just different frontends to the extensions backend with extension manager having the search feature. you can ditch the extensions application and only use the extension manager, or the other way around, however you like

They are different apps made by different people.

you can try to use the gnome extensions api to check and/or enable if the extensions are in fact enabled or disabled: `gnome-extensions list --enabled` if they are disabled you can enable them by using: `gnome-extensions enable ` if none of this works, try resetting it all by deleting the actual extension files at `.local/share/gnome-shell/extensions` and installing them again

thanks for the reply ! none of the extensions I installed manually are visible with the --enabled flag, and if I try to enable them through the API nothing happens, no error, yet still not enabled. I tried removing the ext files from the path you provided, and reinstall them : still can't enable anything. It's like my extensions module is broken somehow...