I have a Dell Inspiron 7548 with a 4k resolution screen. When I first installed Ubuntu on this machine I had a screen flickering issue, but I solved it passing the option i915.enable_IPS=0 to the kernel upon boot (source: Askubuntu and bugs.freedesktop).
But now, after an official kernel update (126.96.36.199) this tip doesn't work anymore. No problem if I go back to 188.8.131.52.
Thank you very much