Because it has only 8MB flash and does not (currently) support mesh, I was planning to donate my RE450v1 to a local charity and I tried to flash it to the original firmware using OpenWRT LuCi. Bad idea. It bricked the device.
I used:
Now when booting the RE450v1 is blinking (central button). Can it be unbricked easily without access to serial console?
Sorry, I gave it to recycling. Anyway, the RE450v1 has only 8MB of flash, too little space and does not support wireless mesh (claims to support it, but /dev/mesh0 does not show). I had to rebuild custom OpenWRT images. Instead I am using two GLinet B1300 and I am very happy. So closing the issue.