From some reason I got the Russion version (HW Rev R1) of DIR-878.
The recovery web interface method does not work for this version. The pre-installed u-boot fails in checksum for any non-russian firmware, including the A1 FW, even via tftp
I've resolved it by flashing the A1 boot loader from https://drive.google.com/file/d/1tR08Gqhp38SlaDjYcRLM-JL3U7xrW6un/view and then flashing OpenWRT + manually installing luci (was not there by default from some reason)
My full notes are at https://workflowy.com/s/openwrt-on-d-link-di/it9O5p5adj1Vwvwb
I wanted to add comments in the Wiki about this R1 variant but could not login. I'm sure I added stuff to the OpenWRT wiki in the past...
Can anyone add this for me or tell me how to register/login?