The combination of both monitors allows me to check each of my designs both on a high-quality monitor, as e.g. a mac user would have, and on a low-quality monitor.
You probably also have encountered websites which are designed for tiny monitors, and end up with text stretched across 40cm (e.g. HN) or websites with razor-thin text that is basically unreadable on cheaper monitors.
As I work in UI/UX design, I want to avoid that issue :)
KScreen is weird, i had a scaling issue that happen if at boot, both my 21"+27" are connected (they are both FHD), but if i boot with 27" monitor then after login connect 21" there is no scaling issue. Maybe that could help you somehow
You can also try to put your PC in Sleep instead of restart each time, if you have a good UPS and some redundancy
Wouldn't a lower resolution result in worse clarity?
I also have a 4k and a 1080p. The 4k is my primary work monitor - i want crisp text. The 1080p is actually a gaming monitor (plus 244hz), since my card can't push 4k for gaming at 244hz hah.
Could i have two 4ks? Yes, but originally this setup was used by my macbook pro, and i wasn't confident it could push two 4ks. Futhermore my 1080p gaming monitor would have to go somewhere, and i'd like to not have two different desk setups.
My setup these days is to scale everything x2 (in KDE or XFCE, currently i'm on XFCE), and then scale my 1080p _down_ via xrandr (as i'm not on Wayland).
Sidenote, Mac handles these two monitors _perfectly_. I complain a lot about Mac, hence me being on Linux at the moment - but these monitor scaling issues were entirely gone in OSX. I never noticed a single scaling issue. Where as on Windows there are lots of quirks, and Linux i could barely get it to work.
Hopefully Wayland makes this experience better.
*(Sidenote: i'm on XFCE atm because KDE on NixOS felt a bit sluggish. Maybe it was just the animations, hard to say. XFCE felt a bit snappier. GNOME was a laggy mess, hah. KDE and XFCE were both good though, XFCE was just a bit better for me on unmeasured performance feel)
Is it? It apparently is not good enough for the main screen.
The thing is that scaling works just fine if all your displays use the same one. Two 4k screens -> awesome. Two fhd screen -> works just fine. It is only the combination of one hires and one lowres screen that is problematic.
So my maybe naive take away is that if you care that your main screen is 4k, then no your old screen is not good enough. And if you think it was good enough, then why did you feel the need to upgrade your main screen?
As I answered earlier: Different screens can be used for different purposes, and different purposes may have different requirements :)
Even if money was no issue and I could have two screens of the same quality, I’d still keep the old screen as a third screen.
For most people, more screens = better, but for me there’s also the fact that to actually design content, you need to be able to verify what this content is going to look like on the devices the users are going to use.
Because I use the main screen for more than displaying docs and chat? And it's a problem to spend large-ish amounts of money just to workaround software problems?
If you don't care about hires, why not simply set the Dell one to a lower resolution and not worry about scaling at all?