Switching to Vivaldi browser, I could easily install the plugin in the desktop version of Vivaldi but not on my smartphone with Vivaldi for Android…
I asked on the dedicated Vivaldi forum here and for who’ll ask him/herself the same question the answer provided is working good:
You can’t install third-party password managers on the mobile version of Vivaldi, but if the password manager has its own Android app, you can make it work together with Vivaldi.
In Vivaldi make sure you’ve enabled “Use Android autofill sevrices” in Settings > Autofill services and in Android’s settings enable Nextcloud as the preferred autofill service (there’s a shortcut to it in the Autofill services settings section in Vivaldi).
For this to work, the apps would need to support Android’s AutoFill. But, as I said, I don’t have any experience with Passwords myself, so you’d have to test them out, or maybe someone else here who actually uses one of these apps can say more about it…
Thanks for coming back and sharing the solution. I wasn’t aware that Vivaldi for Android doesn’t support third-party extensions like the desktop version.
Using the Android autofill service with the Nextcloud Passwords app makes sense, and it’s good to know it works as a replacement. Hopefully this saves others from spending time trying to install the browser extension on mobile.