If you mean the TL-MR6400 (WR6400 doesn't seem to exist), then yes, the v5 image works for v5.3, at least I didn't encounter any issues with flashing, lan, wan, wwan or wifi after installing OpenWRT 23.05 a few weeks ago. This thread also confirms that it works.
Though if you don't need WWAN (lte), there should be better options for an OpenWRT-supported router.