First of all, many thanks to the maintainers for their ongoing efforts on the OpenWrt project.
I've just upgraded my GL.iNet GL-B1300 to v19.07.3 (from here) and that soft-bricked the router. As I was upgrading, there was this warning which I had overruled. I did untick
 Keep settings:
The router did go through the normal flashing process but after a reboot it just had not come back to life with all LEDs off. So I successfully reverted it back to v19.07.2 using UBoot TFTP method. Then I tried flashing v19.07.3 directly via UBoot, with the same results as before. So I've gone back to v19.07.2 again.
I'd be happy to help investigating it further if I could get some guidance
Updated, the same thing happened to my travel router, TP-Link TL-WR902AC. Had to rollback to v19.07.2 via TFTP. Coincidentally, both routers are Atheros SoC-based.