Hi followed method 2 below and now have a rebooting router.
http://lede-ac58u.zyxmon.org/HowToFlashENG.html
First upload this one below and then flashed it... It said finished ok and said reboot manually.
[openwrt-r1834-0f04829-ipq806x-asus_rt-ac58u-squashfs-flash-factory.trx]
Look at the router and saw it was just repeatedly power cycling every 30 secs or so. Tried a reset, still the same state.
Bricked? or A way out?