I see the GL.iNet GL-XE300 Puli is not yet officially supported but a search of the forums shows at least one person is using it:
Based on the specs, the most similar device seems to be the GL-AR300M. They have the same proc, ram, and flash specs, as well as the same brand. The current supported version is 19.07.7, but the DB says NAND is not supported unitl after 19.07. However a comment states:
"Flashing to the 128MB NAND flash is supported in Snapshot ath79 at time of writing, removable external antennas on "ext" variant"
Further, there is a GoldenOrb version for the AR300M. Should I proceed to flash the AR300M onto the XE300, and if so should I go OpenWrt or GoldenOrb?
Wow, I really failed to do my homework before posting here. The default interface seemed too simple and dumbed down so I jumped to the conclusion I need to wipe it and put a vanilla image on it. All I was missing was that I had to install luci, and I would have known that if I had thought to check gl's docs first.