Is there a way I can use backing tracks from youtube or other apps through almost kinda like how discord has set up with their “rythm bot”.

There are at least 3 ways of doing this. Before explaining I would like to draw attention to jammr's Terms & Conditions, which says “You must not play copyrighted audio that is not compatible with this license (Creative Commons Attribution-ShareAlike 3.0) over jammr”.

If you have backing tracks that are licensed appropriately then you can try the following:
1. If you are using a mixer then you can connect a device that plays the backing track into the mixer without changing anything in jammr.
2. Load an audio player VST plugin or AudioUnit into jammr (Settings | Effects Plugins).
3. Use virtual audio cable software like Soundflower, JACK, Blackhole, VB-Cable, etc to send audio into jammr.