Hello, everyone. I want to ask you something. I am using Ubuntu Mate 20.10 and I received a notification that I can upgrade to Ubuntu Mate 21.04. But I am using Ubuntu Mate 20.10 with the possibility of usb booting support. Is this (usb booting) available in Ubuntu 21.04?
You should upgrade because security updates and support for interim releases like 20.10 are only for 9 months. I think USB boot is provided but you will have to research that further on the main Ubuntu Mate page and/or Raspberry Pi page.
Yes, I upgraded to Ubuntu Mate 21.04 on my RPi 4GB and it works when booting from a SSD via USB. You have to be careful with other USB connections though and even with a powered USB hub what I find works best is to boot with the SSD plugged in directly and then add the powered USB hub for other USB peripherals (don't think this is any reflection on Ubuntu Mate but is a RPi limitation).