Seems like at this point, we will need to highly recommend flashing a different bootloader in the wiki. Most of these bricks seem to be on RD23 though.
This was recommended as a replacement for OpenWrt U-Boot and it apparently supports the stock layout too: What's your favourite cheap LEDE/OpenWrt device? - #735 by erayrafet
I don't use it myself though, so I can't vouch for it.
Like in the thread you linked (more specifically my post in it), did you do the steps mentioned in Basic Configuration?