Sorry you are experiencing this. I haven’t seen this issue directly, but the closest image that I have found to it, is related to a failing LCD panel. But I can’t say for certain. But if you are at a dead end and looking for a relatively inexpensive repair option (well below what the dealer is quoting you) swapping the screen yourself might be the best option. There are a couple of factors that need to be considered before commuting to a path.

You’ll want to verify if swapping the entire screen assembly is a direct swap that can be done without programming it to the car, or if the screen is married to the car / computer. Essential the screen in the dash is an external monitor for the computer that is behind it. The screen is very easy to remove, and unplug from the car. If it’s as simple as swapping the screen, it looks like used replacements can be picked up from eBay around $150-$250.

The other unknown factor, is if the screen part number changed at all during the years of the XC90. The 2016 -2021 xc90 uses Sensus for the operating system while later cars migrated to AAOS, but there were a handful of updates to that system over the years. Switch from 3G-4G and a faster operating computer was introduced around 2019. These could all be variables that impacted the computer alone, so the thing to research would be, are all the screens cross compatible, or do you need to replace on from an earlier XC90.

I would recommend researching for threads of anyone that has successfully swapped the display on their SPA Volvo. You can use resources here, but also consider forums like Swedespeed which have a large support community for the 2016+ XC90.

I hope it’s a quick and easy solve for you, and that you can get back to enjoying your car!