I'd been having problems with the scale of the VLC interface at 4K on my Linux machine (KDE Plasma, Wayland).
I found a solution from a mix of previous solutions for Windows and other Linux solutions which did not work for me. The problem is with QT (which is used by VLC) and the linux solution was to put extra lines in the /etc/environment file but I found while this fixed VLC it mucked up all other QT apps including my Plasma desktop.
The solution is to use VLC flatpak and set the environment variables for the VLC flatpak app only using Flatseal or the Flatpak Permission Settings in KDE.
Add two Environment variable:
Variable name: QT_AUTO_SCREEN_SCALE_FACTOR
Variable value: 0
Variable name: QT_SCREEN_SCALE_FACTORS
Variable value: 2
For the second variable, scale_factors, set it to match the scaling you use on your desktop. 1.0 means 100%, 1.5 is 150%, 2 is 200% and so on. My desktop is set to 225% scaling, so I set mine to 2.25 and it worked. In the end I went up to 3 for VLC because I liked the interface even more at that scale (it's a living room TV Linux machine)
Hopefully this will help other people using VLC in Linux.
If you don't want to use Flatpak, you can add the same variables to your /etc/environment file (in the format QT_AUTO_SCREEN_SCALE_FACTOR=0) but be warned you may get jank elsewhere. This may be less problematic outside of KDE Plasma as that is QT based desktop environment. For Windows users it is a similar problem with QT and there are posts out there about where to put the exact same variables to fix the problem.
Ubuntu does work and is a decent distro in many ways. The problems are around how canonical leverages things for its own financial benefit for the detriment of users and the Linux community.
A good example is Snap. It is forced on users - even Firefox is a snap on Ubuntu. This is not an efficient way fo end users to run their system or their most used software.
Instead of making the builds available as standard software, users have to use the Snap or go hunting elsewhere for builds. That's anti-user and is identical to how Microsoft behaves with windows. It doesn't do things to benefit users, it does things to benefit Microsoft.
It's arguable whether what snap does is actually worth the overhead - I can see that it is more secure in many ways. But then so it Flatpak, and that is more universally used for desktop software across Linux distros. Snap has some inherent benefits for server side use but then why force it on end users where it is not as good as Flatpak in many ways? Or Appimage?
So Ubuntu is fine in many ways, but why bother when you can go for alternatives and give the best of both worlds? Mint is an Ubuntu based distro without snap and other canonical elements. I used mint for ages, it's great and there is a reason it's so popular.
I've moved on to OpenSuSE now but the Ubuntu ecosystem is fine, it works well for many, and it's very well documented and supported which often works downstream in Mint and others. It's just Ubuntu itself thats a bit crappy due to the decisions made to suite canonical rather than what users want or would suit them best. In the end it all comes down to personal choice and what people are willing to accept from their distro.