I don't know if this will help but I had a similar issue.
I have an MSI GS66 and I'm duel booting pop and windows. One day I was trying something and switched my graphics on pop to discrete and when I changed it back to integrated I just got a blank screen on boot up.
So I went to Windows to see if I brick my PC somehow but it worked fine and would switch cards fine. I was able to boot into pop with the discrete card but when I changed it to mshybrid in windows just a grey screen.
How I fixed it was go into the BIOS, changed the graphics from discrete to mshybrid then will it was booting hit the spacebar a bunch and I think it brings up systemd. Anyway it gave me three options first was to continue in current kernel the second was to boot into older kernel and third was firmware. I picked the older kernel and it booted just fine all my apps and stuff were loaded and working.
