I've built an image for the WNR2000v3 that should run 18.06.4 with no bootloops, no lost settings after reboot. You can upgrade directly from a previous version of OpenWrt using the sysupgrade .bin file.
This image includes LuCi (GUI), IPV6, SQM - no PPP. A build manifest is available in the download folder.
If you end up installing, please let me know how it works for you. I don't have a WNR2000v3 to test it on directly - but it runs great on my almost identical hardware, the WNR1000V2.
More information on these builds.