I was able to install Lubuntu and log in:
default Username: linkstar, Password: linkstar
Root Username: root, Root Password: root
(from the “Install Operating System” page linked above by Seeed-Liu)
However, only eth0 and eth1 are available. Neither the 2.5G (eth2 and eth3) nor the wifi seems to be available. I upgraded to Ubuntu 22.04.2 LTS and upgraded all software packages as much as possible, but it’s still using a 4.19.219 kernel.
The wifi appears to need kernel version 5.12 or newer, according to MediaTek MT7921 802.11ax PCI Express Wireless Network Adapter
The 2.5G Ethernet appears to need kernel version 5.4 or newer, according to Realtek RTL 8125 - LinuxReviews