Upgrading LEDE on Asus RT-66u

This router does not have a special sysupgrade image. Is it possible to upgrade from an older LEDE version to a newer one with the one image available? If not, what's the best way to go about this?

https://lede-project.org/toh/hwdata/asus/asus_rt-n66u_b1

Thanks. Both the designated factory install and upgrade links are identical. So for some routers, including this one, you can just flash the new image and don't need a special sysupgrade image? I am asking because I wasn't sure if the upgrade field on the tech data pages were just filled with the factory install image link by default if no other link had been set.

https://lede-project.org/docs/guide-quick-start/sysupgrade.luci

The instructions here indicate that you must either use a sysupgrade image or if one is not available, follow router-specific upgrade instructions, which are not available for this router as far as I could find.