Upgrade Sketch to Buster (or Bookworm)

Update system

sudo apt update
sudo apt upgrade
sudo apt full-upgrade
sudo apt --purge autoremove

Reboot to reload any kernels

sudo shutdown -r 0

Update sources to buster w/ sed search and replace:

sudo sed -i 's/stretch/buster/g' /etc/apt/sources.list
sudo sed -i 's/stretch/buster/g' /etc/apt/sources.list.d/*

Verify

cat /etc/apt/sources.list

Update and upgrade

sudo apt-get update
sudo apt-get upgrade
sudo apt full-upgrade

Reboot once more

sudo shutdown -r 0

Verify

uname -r
lsb_release -a