Ubuntu 20.04 - different scaling for multi display setup

Question

I have 2/3 monitor setup

nr #1 - 5120x2160 (21:9) AKA "5K"

nr #2 - 1920x1080 (16:9)

nr #3 - 1920x1080 (16:9) - connected and used only occasionally

display setup

It`s messy. Default resolution detected by system for #1 is 3440x1440. After switching to the full native resolution of "5K" it looks way better but UI elements and text are uncomfortably small.

When I change scaling for #1, #2 is changing as well :/ Also, I'm glad to see Fractional Scaling build in Gnome Display Settings but it's buggy in my case:

#1 set to 150% scaling - as you can see in this screenshot (although it doesn't reflect the problem 100%) its messed up. On #2 I can go only to half the height of the screen where the top bar is being displayed. Wallpaper is messed up. It's unusable.

Wayland is unavailable for me since I use Nvidia GPU. I wouldn't like to lower my resolution on #1 as a workaround.

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So my question is:

How to set up #1 to 200% while keeping #2 (and #3 at some occasions) at 100%.

Solution

I solved this question simply installing gdm3 and choosing this display manager instead of lightdm which was the default installation of ubuntu session on 20.04 release. Now it is possible choose different ad fractional scaling on multiple monitors (eg. native 1920x1080 and 3840x2160 on auxiliary monitor)

Comments

[Admin]

It is not working as it should. You could try using Wayland instead of the old Xorg: that may work better with modern setups using different monitors with different resolution. On the log in screen, click the cog to choose the Wayland Ubuntu session. You can always return to Xorg later using the same procedure.

[Admin]

@vanadium 1. I don't see Wayland, instead, I have Gnome Classic or Ubuntu to choose. Apparently, if I'm using an Nvidia GPU (which I use) - Wayland is not avayilable for me (cause of closed source drivers :( ) Gnome Classic didn't help :( Same scaling problem and way uglier ;p

[Admin]

did you manage to find a solution to this?

[Admin]

@tocallaghan sadly no. I had to turn my resolution down so the scaling could be same on both displays.

[Admin]

This has been going on for so long, why they haven't fixed it, I don't know, but it makes me not want to use Ubuntu anymore.

[Admin]

With Nvidia GPU, using NVidia X Server Settings with the approach described here worked perfectly. I'm using a dual monitor setup with a 5k Dell display and a 2520x1440 secondary display.