Rk3588 boards now share the same linuxfamily as rk3568 and rk3566 boards. It means rockchip-rk3588 kernel won't get update longer. Here is some steps for migration:
sudo sed -i 's/LINUXFAMILY=rockchip-rk3588/LINUXFAMILY=rk35xx/g' /etc/armbian-release
sudo apt update
sudo apt install linux-image-legacy-rk35xx linux-dtb-legacy-rk35xx linux-headers-legacy-rk35xx
sudo apt remove linux-image-legacy-rockchip-rk3588 linux-dtb-legacy-rockchip-rk3588 linux-headers-legacy-rockchip-rk3588
NOTE: The steps are currently for beta branch only. Don't try on stable branch.