I'm using an ACER Predator G3-710 and just installed my Ubuntu alongside Windows 10 on a second SSD-Card that was previously empty. Everything went fine but after restarting my PC it always boots into windows immediately and won't show the Grub menu. I also can't find Ubuntu in my BIOS Boot settings.
Solved: I had to disable save boot in my BIOS settings and change the bootpath using this article.
By running this in my terminal
bcdedit /set {bootmgr} path \EFI\ubuntu\grubx64.efi
Thanks for all the help! :)