I recently purchased a new Dell Inspiron 16 Plus (Intel i7 11800H, RTX 3060) and I want to use Ubuntu 20.04 in dual boot.

There were issues with both gpus from the start, what helped so far to mitigate the problems was adding 

GRUB_CMDLINE_LINUX_DEFAULT="quiet splash i915.enable_psr=0"

to /etc/default/grub (found in this forum) and disabling secure boot. The NVIDIA gpu works fine now, but there is screen tearing (see photo) when I use the Intel gpu, for example when I drag a window across the screen. Youtube videos in 3k resolution also have lags and do not run completely smoothly. I noticed that this problem only occurs with fractional scaling (e.g. 125% or 150%).

In Ubuntu forums it is often suggested to add 

Section "Device"
    Identifier "Intel Graphics"
    Driver "i915"
    Option "TearFree"    "true"
EndSection

to /etc/X11/xorg.conf.d/20-intel.conf, but this results in all sorts of graphic artefacts and made my system unstable.

Did anyone experience similar issues and managed to fix them?

screen tearing on intel gpu