What monitor models are known to not have issues with Display Scaling ?

[Bobo]

Was thinking of upgrading to a 360hz or 500/540hz monitor, but a lot of them have issues when you use custom resolutions, the image is quite blurry.
Can you recommend a few models that don`t have that issue ?

[kyube]

Was thinking of upgrading to a 360hz or 500/540hz monitor, but a lot of them have issues when you use custom resolutions, the image is quite blurry.
Can you recommend a few models that don`t have that issue ?

The issue you're referring to in the OP are not what you're asking in the title. They are 2 distinct issues.
To be able to have “blur-less” scaling on lower than native resolutions, you have one of the following options to choose from:
1.) Run “Integer scaling” (doesn't achieve total PPI of display)
2.) Run “No Scaling” (Nvidia) | “Center” (AMD (retains PPI of display, changes viewport according to resolution chosen) [best approach]
3.) Run DLSS or Nvidia Image Scaling (Nvidia) | FSR (AMD) (doesn't retain PPI, doesn't resort to billinear scaling which means static sharpness is adequate but motion sharpness suffers depending on native resolution)

Note: 1.) doesn't work with displays that employ DSC (which 480-540hz panels all do, only 540Hz tandem OLED & 600Hz rapid-TN are exempt from DSC at these refresh rates)

You also might be referring to the fact that DSC exists on these 500-540hz panels, hence why users report having “issues with custom resolutions” (not being able to run them at all). This isn't that big of a problem as users might make it seem out to be.
This is solvable by either option for a display with full BW (HDMI 2.1 FRL6 or DP2.1 UHBR20) or using Toasty's SRE
The 600Hz Rapid-TN panels (242R X60N, XG248QSG, AG246FK6) on HDMI 2.1 (FRL6) should be able to run @ 540hz without DSC.
The new 540Hz Tandem W-OLED panels or 500Hz QD-OLED panels employ DP2.1 UHBR20 (able to run 1440p@480hz@10b without DSC)

The only rational option to avoid “blurriness” is to stick to either play on native resolution (1080p in this case) or use “No Scaling” (Nvidia) | “Center” (AMD) to avoid the higher GPUBusy penalty that 1080p may cause on your system.

This doesn't consider the topic of latency differences between different scaler IC implementations.
To avoid the sheer randomness of them, avoid relying on Display Scaling and instead use GPU Scaling.

[Bobo]

On my current monitor XL2546k, i am using No Scaling in nvidia control panel, the issue persists.
The problem is the monitor itself, the scaler from what i`ve read on the internet, so my reason for making this post is to get recomended a few models that don`t have this issue.

[kyube]

On my current monitor XL2546k, i am using No Scaling in nvidia control panel, the issue persists.
The problem is the monitor itself, the scaler from what i`ve read on the internet, so my reason for making this post is to get recomended a few models that don`t have this issue.

What “issue”? There are no issues if you are using GPU scaling.
Display scaling hasn't been relevant for over a decade now. It has been made redundant by GPU scaling (QL on OGL API).
The only data set I'm aware of is ancient (a decade old) (source: flood / qsxcv) on ancient HW and on an ancient game.
Whether this applies to modern HW is unknown, as microsecond precision (a requirement for these endeavours) input latency tests are rare.
Yes, ~120µs is an eternity to computers.
I cannot say for certain that it can be applied to every single system, every single graphics API & whether this value is applicable to today's scenario.

Why use the one which is more random (display scaling) over a more consistent one (GPU scaling)?

I'm very certain that any new +360hz display you choose will not have the scaler used by the XL2546K, I've found this conversation which you might be referring to

As far as I'm aware, these are the brands of scaler IC which are known on the market:
MStar (old, used in 144hz TN's), TPV, Realtek (very likely what's used in the XL2546K), Novatek, Mediatek (e.g.: used in new Pulsar line-up), GSYNC FPGA (deprecated)
There's also Skyworth, Suzhou Lehui, Qisda (parent company of BenQ), but I'm not aware whether they make scaler IC's or TCON's.

Information on which particular displays implement which scaler IC is usually hidden, meaning that it requires manual disassembly of the chassis.. which most reviewers don't want to do.
Sometimes, some service menu's do make note of which scaler IC is used.
The only reviewer I know of which attempts display disassemblies is snowman (@09:47 for service menu)
In this particular case (XL2546K), there's no mention of scaler IC used.

Here's an example of the XL2540