The procedure to update your daily Ubuntu Mate for RaspberryPi to 21.04.
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/usr/lib/ubuntu-release-upgrader/check-new-release-gtk
sudo apt install fcitx-config-gtk
sudo nano /boot/firmware/config.txt
over_voltage=6
arm_freq=2000
gpu_freq=700
gpu_mem=128
/usr/lib/ubuntu-release-upgrader/check-new-release-gtk
apt –installed list
echo $XDG_SESSION_TYPE