Hi

Have you tried following the guidance in this support article?:

https://support.mozilla.org/en-US/kb/extended-add-support

Hi Have you tried following the guidance in this support article?: https://support.mozilla.org/en-US/kb/extended-add-support

Yes, I'm already using Firefox Nightly with my own “Custom Add-on collection.” This error was like that since Mozilla introduced “Custom Add-on collection.”. I just need video downloader in Firefox really bad

The error message should be clear why it fails to install

Even using that approach, not all add-ons are supported in Firefox for Android at the present time.

When I look at the versions page for Video DownloadHelper, the only reference to Android support is for this much older release:

Version 7.3.9 Released Mar 25, 2020 - 761.83 KB Works with firefox 42.0 and later, android 48.0 and later

I don't know whether that version really did work on Android, or the checkbox for Android was selected accidentally during the new version upload process.

For comparison, the versions page for user script engine FireMonkey indicates

Latest version Version 2.66 Released Nov 9, 2022 - 1.11 MB Works with firefox 74.0 and later, android 74.0 and later

Maybe you can find a video downloader that mentions Android compatibility. It doesn't seem easy to find in a search.