I bought this router with the intent of installing OpenWRT (I already have Netgear R7800 running OpenWRT much better than the OEM Netgear firmware). I chose the Linksys because of the device page that describes "OEM Easy Installation". From my experience, the information on the Linksys page is inaccurate. If your router arrives with firmware 1.1.4.170630 or higher, you will NOT be able to downgrade it back to 1.1.4.169978, or to install third party firmware "the easy way". This is because Linksys began to sign the firmware starting with version 1.1.4.170630. The only situation that easy installation is applicable is if your router has version 1.1.4.169978 or older installed. If you have newer firmware, the only way to install OpenWRT is by opening the router, connecting special cable, etc. This is much more involved that merely flashing a file from the router's GUI. I wish the information on the device page was more accurate, and maybe put a warning there.
You are most welcome to edit that very same page and add your personal experience in as detailed a way as you did here. Nothing like first hand information to help others further along.