I have been able to install Ubuntu-Mate successfully on a RPi 5.
However, you need a RPi 4 to get it up and running.
- Download the Ubuntu Mate 22.04 image
- Install onto a good quality SD Card or SSD via RPi-Imager
- Boot the drive with your RPi 4 and install as normal
- Reboot and install all current updates
- You should now get an option to upgrade to 23.10. Do this, it will take about 90 minutes.
- Download gldriver-test from here and install. You need this to get graphics working on the RPi 5.
- Shutdown, move your drive to your RPi 5 and boot up. You should now have an up-to-date version of Ubuntu Mate running on your RPi 5.
Enjoy.