Hey, I can confirm the bizzare dedicated GPU behavior on my 9560. Bumblebee with bbswitch hinders with GDM (for Gnome users). Personally, I’m an Arch user, yet experience similar issues with the 1050 running on Ubuntu 18.10. Options to get a stable system are,

• Install Nvidia (and bumblebee without bbswitch, which is technically useless without the latter) and forget about the power consumption ’cause you’re not getting any of it!
• Or (like me), install Nvidia (optionally with bumblebee but not bbswitch) and blacklist the nvidia module with a kernel parameter and enjoy power savings (I’m at ~8W with about 7h at 80%) while you let your GTX1050 sleep.

Nice post and happy to know that the XPS 15 9560 get’s a good deal of support.

Cheers!