Upgrading to Bullseye (troubleshooting Armbian 21.08.1)
Upgrading Helios64 from Armbian Buster to Bullseye (see below) works as expected on my system.
However, I am using systemd-networkd and just a few services (nextcloud, netatalk, etc. and not ZFS)
EDIT: Upgrading Buster installations to Bullseye also works fine if you use network-manager, even if you have a bridge configured (using bridge-slave; binutils-bridge).
# cat /etc/os-release
PRETTY_NAME="Debian GNU/Linux 11 (bullseye)"
NAME="Debian GNU/Linux"
VERSION_I
Where did you find the required 21.05 kernel packages ?
For the downgrade you would need those:
armbian-bsp-cli-helios64/buster 21.05.8
armbian-config/buster,buster 21.05
armbian-firmware/buster,buster 21.05
linux-dtb-current-rockchip64/buster 21.05.4
linux-headers-current-rockchip64/buster 21.05.4
linux-image-current-rockchip64/buster 21.05.4
EDIT: I found them here: http://armbian.hosthatch.com/apt/pool/main/l/linux-5.10.43-rockchip64/