It works on ubuntu. But not on the snap version of firefox, which is installed on the system by default. Download the browser from the official site.

So, It's a very good extension and it does what it needs to do. The only thing that is a bit painful is that it requires a bit of setup to do, particularly if you have the portable version of uGet. But overall once it's all setup it works very well.

For all of you, that say the addon didn't work, look here
https://github.com/ugetdm/uget-integrator/wiki/Installation . You must install this! It works really fine!

not working

Perfectly integrates uget for all my OS's. Used it since before the author was cool and all integrated. :) Really, nice work.

Interruption is quirky (at least on Linux). Sometimes FF starts the download then it gets paused while uget interrupts and ff is stuck on paused.

Sometimes it doesn't pause, and it ends up being downloaded by both programs.

Otherwise, great. Still going to continue using it.

does not interrupt downloads in firefox, you have to put the link manually to start downloading