After I upgrade the TP-Link TL-WA901NND v4 from 18.06.5 to 18.06.8 my Luci enviroment broke.
/usr/lib/lua/luci/dispatcher.lua:234: /etc/config/luci seems to be corrupt, unable to find section 'main'
stack traceback:
[C]: in function 'assert'
/usr/lib/lua/luci/dispatcher.lua:234: in function 'dispatch'
/usr/lib/lua/luci/dispatcher.lua:127: in function </usr/lib/lua/luci/dispatcher.lua:126>
This is due to LUCI now rendering on the client end. If your using a custom theme your best bet is to install the bootstrap theme and set that as your current theme.
The theme your currently using will need the new changes added.
This change seems to be on all branches be it 18.06.xx 19.07 or the master branch.
Easiest way is to install WinSCP. Use it to connect to the router with it then go to /etc/config and edit the Luci or system file save the file and reboot.
If you look I said go to /etc/config and then edit the Luci or system file that's within that set of folders. You simply change the theme name to bootstrap.
So I've been flashing 18.06.8 on a Xiaomi MIR3G (ramips/mt7621) and on a TP-Link TL-WR1043ND (ar71xx/generic) to rule out target specific issues and LuCI worked as expected. I am unable to observe the crash.
When you say you upgraded, did you reflash with an 18.06.8 image or did you perform opkg upgrades?
I mostly upgrade between my own builds ~ 1 time each month and I usualy keep the settings (because I'm too lazy to remake them) and I don't remember an issue with Luci crashing.
I did had an issue last year with my builds restarting the router every 2 min (it was stable only if I was clearing all the settings, the smallest config change was triggering the reboot every 2 min) but it looks like Ubuntu messed up something in their kernel, reverting to an older kernel on the build machine generated builds that were working without problems. (dmesg on the build machine was showing a crash related to igpu, something that well was happening ~2015 based on my google searches...). I changed to Manjaro due to this particular issue with Ubuntu (no issues with Manjaro and latest stable kernel, no crash in dmesg on the build machine).
L.E.: I build it from 0.
In the next days I will compile to have the last commit (it was planned anyway) and see if there are any problem.
If you run custom builds, the most likely fix for /usr/lib/lua/luci/dispatcher.lua:234: /etc/config/luci seems to be corrupt, unable to find section 'main' is to manually clean and rebuild rpcd using make package/rpcd/clean world V=s then reflash the resulting image.