Upgrade to debian11 from 10

# apt update
# apt upgrade
# apt full-upgrade
# apt --purge autoremove

deb http://mirrors.linode.com/debian bullseye main
deb-src http://mirrors.linode.com/debian bullseye main
 
deb http://mirrors.linode.com/debian-security bullseye-security/updates main
deb-src http://mirrors.linode.com/debian-security bullseye-security/updates main
 
# bullseye-updates, previously known as 'volatile'
deb http://mirrors.linode.com/debian bullseye-updates main
deb-src http://mirrors.linode.com/debian bullseye-updates main

Then update,

apt full-upgrade
reboot