I want to use a small USB mixer with my Mate desktop so I can use my XLR mic and get better audio quality. I have installed Ubuntu Studio but I am bewildered by all the tools and settings. Is there anyone out there who could help me set up something simple?
Thank you.
Your details are unclear.
You mention Ubuntu Studio, which mostly used the Xfce desktop, until they switched to KDE Plasma a number of releases ago. You've not provided release, but how does MATE desktop apply to this? Was it a Ubuntu MATE install on which you added Ubuntu Studio packages using ubuntu-studio-installer, but even then results will vary on what you started with (esp. release). For best results I suggest you're clear with details.
Ubuntu MATE switched to PipeWire back with 22.10 (Ubuntu Studio didn't switch till 23.04), but you may find some PulseAudio controls are still useful. Starting point is still what Ubuntu MATE release you're using.
Hi, @Quenyar and welcome to the Ubuntu MATE Community!
Release 24.04.3 LTS (Noble Numbat) 64-bit
Kernel Linux 6.17.0-14-generic x86_64
MATE 1.26.2
I got you! 
I have a similar setup. I am using a Behringer C-2 condenser mic (which is XLR) and a Behringer UMC202HD audio interface.
It sort of works out of the box ... except in the ways that it doesn’t. But thats just my particular audio interface.
With some details about your audio hardware I might be able to say more.
For recording, Audacity is a useful tool but has a steep learning curve.
For streaming, OBS Studio is solid.
If you want to mess about with live filters, Carla is reasonable and there's also EasyEffects which is more beginner friendly.
If you have my luck (i.e. bad luck) you may have to mess about with PipeWire to get the channels mapped correctly on the audio interface. But fingers crossed you won't! 
CAD Audio MXU2 Multipurpose 2-channel Analog Mixer with USB interface.
Groovy. When you say you need help setting up something simple - what do you mean exactly? Can you see the audio device in the Input tab of Sound Preferences?