Flashing OpenWrt on Linksys MR8300 - partially bricked

Thanks a bunch for helping me validate.

Yes, you are spot on. From "Factory" Linksys firmware, navigate to that URL and upload the factory.bin file. Luci and some additional apps are already included, I think you will find it's a complete user experience covering most bases out of the box.

One thing to note, if you didn't already know, is that these Linksys routers have dual firmware partitions, 1 and 2. So when you flash from stock linksys, for arguments sake we will say linksys is on partition 1, then OWRT will now be flashed onto partition 2. It normally round robins, so if you were to flash a newer OWRT build using the upgrade method from within OWRT, that would overwrite partition 1, where stock is, leaving you with both 1 and 2 having OWRT.

What I advise to do as a fail safe is after you flash the image above, you can use the included package I already baked in called "Advanced Reboot" (It will be in the Menu already for you). This will tell you what partition you are on, and gives you the ability to click a button to reboot back to the alternate partition. From there I would advise flashing your new OWRT build back from the Linksys side using the factory.bin file. This way you always have factory on one partition and OWRT on the alternate. Keeps things clean.