Works fine with your mods for me:
Can you upload the save somewhere?

...and now it's working. Before, it wouldn't even late me place the engine. It just gave me a small box for it on a rail (not the full-sized locomotive) and wouldn't let me place. Of course, now I'm getting the same issue I ...

I can't even place the dang locomotive. When I click on a track, or on an engine, nothing seems to occur. Factorio 15.10

Are you using any other mods? What FARL version?

You have to get in the locomotive for the GUI to show up

No UI came up for me.

YARM_0.7.201
Squeak Through_1.1.7
tree ...

I can't even place the dang locomotive. When I click on a track, or on an engine, nothing seems to occur. Factorio 15.10