I think they talk about the cloud and ad services integrated in GL.inet firmware, and the fact that the used openWRT is….old (23)
ANyway, if you want a clean vanilla OpenWRT install, don’t follow advise above.
(because you can better use Uboot with UBI image to be sure it goes okay.)
DO NOT CONTINUE READING IF LUCI IS COMPLICATED AND YOU CANNOT WORK WITHOUT GL.INET WEBINTERFACE.
Prefer to download the UBI file, not the BIN file.
So search for “GL.inet” or modelname of your router in the 25.12.0rc2 (or 24.10.5 for stable release) section (not snapshot) of the openwrt firmware selector.
Select your device (not all GL.inet routers are supported).
Then download the “FACTORY (FACTORY.UBI)” file.
After downloading go prepare:
1:
Write down(or copy to text file) the exact Wifi Wlan SSID (Network name) for 2.4Ghz and 5GHz Wifi. (sometimes they both have same name), also the Password used by 2.4GHz and 5GHz wlan’s. (can be different, often the same). Write down security type if you know it. Like wpa3 sae security (or wpa2 if you have device with older wifi software)
Because if you configure the same on Openwrt, then you don’t need to reconfigure your wifi devices.
2:
The computer that has the FACTOY.UBI file need to be connected with the GL.inet router with a network cable! Be sure you configure the ethernet connector(rj-45) from the computer with fixed ipv4 settings:
IP 192.168.1.10
Subnetmask 255.255.255.0
Gateway 192.168.1.1
DNS 192.168.1.1
When done. Be sure you want a GL.inet router without GL.inet webinterface (so only Luci).
So no “simple” webinterface for configuration, but Luci webinterface “to configure everything” with a learning curve.
If you want that, then continue 
3:
Remove all cables from GL.inet router that has support for OpenWRT
Connect one ethernet cable to the LAN1 port of the router, and the ethernet/rj-45 connector of the computer that you prepare in step 2 and has the FACTORY.UBI image file.
Get your GL.inet router in Uboot mode, click here.
Then on the computer, open webbrowser and use address 192.168.1.1
The Uboot pge loads, and you can select the FACTORY.UBI file and upload it to the GL.inet router.
When uploading is done you can close webbrowser.
Now wait a few minutes (like 3).
Then reopen webbrowser and goto 192.168.1.1.
And you see that Luci loads from OpenWRT.
Login without password, and after that set a new login password for root.
Then follow this to get wifi configured and on (wifi is off by default), and be sure you use SSID and password taken from step1.
For more questions, goto forum of OpenWRT, and search for your question, because someone has probably already found a solution.