I switched my old HP LV1561w monitor with an Acer monitor, which is also old btw.
Everything was working fine for the first couple of hours. The issue started when I tried to power on my machine the next day, everything seems ok up until the splash screen. Then it started to show “Input Not Supported”. I tried booting from a live-usb and it’s working fine , I even switched my HP monitor back in and everything is fine there too. I reinstalled the whole os with the Acer monitor with no error but the same issue occurred after the splash screen. I’m using amd fx6300 with 4gigs of ram and gtx1050 with the latest non-free driver and I’m using the LTS kernel 5.4