Android Gecko (Firefox): "open a local file" doesn't work

[WofWca]

1. Tap the three dots -> Add-ons -> Jump Cutter, the extension's popup will open
2. "open a local file"
3. Tap on the page to open the file selector
   Nothing happens when you select a file.

I have tried remote debugging. It seems that the local-file-payer page simply closes when the file picker gets opened.

A workaround is to open the local file player directly in a separate page moz-extension://<your extension installation UUID>/local-file-player/index.html. But this doesn't entirely work either. You can open a file but for some reason the video doesn't have sound.