Hey, I recently upgraded to 19.07 ath79 from 18.06 ar71xx with sysupgrade -f ssh command on my secondary WR740N v4 ap/router, just to use new NextDNS luci app for encryption and forward my DNS queries to TPLINK.
Everything went fine but the System -> Software tab is missing. I also did reboot, reset but still same. How can I fix this?
If you had used the -n argument, that would not have preserved the settings (the -f only forces the update, which is necessary because you were changing target image types).
When running major upgrades, it is recommended to not preserve settings, and further, because of the ar71xx > ath79 transition, it is possible that there will be other issues related to the older settings.
Try the following:
Make a backup (you can restore later)
use either ssh or LuCI to reset to defaults and reboot
Once the router is in a true default state, check to see if the software item shows up again.
Restore your backup* and then check to see if the software tab goes missing
*I'd recommend not restoring the backup, in general -- you're better off just recreating your settings (using the backup as a guide/template, if you need it) because there may be some low level changes that need different base level settings (for example, unrelated to this base issue, the /etc/config/network file on some routers may have some major changes to the switch and interface configs).
I don't care about the backup as its only running as AP bridge mode, so setup would be 1 minute for me. I reset it to factory and still same no Software tab...
Ah. Tiny! That is why. Your router is too old and too constrained to run the latest version with all of the normal features. You wouldn’t have space to install anything anyway, given that you have just 4MB flash and 32MB RAM.
The solution is to either roll back to an earlier version of OpenWrt, or better would be to get a new router.
Yes you've flashed a third-party build which apparently does not include opkg. This is a common thing to do with 4 MB devices since there won't be space to install anything more anyway. Such a build needs to meet your use case, or you could try to make your own that does, since you can't add any packages at runtime.
OpenWrt has stopped making release builds for most or all 4 MB devices since the standard release group of packages does not fit the flash.
It should be noted that a dumb AP doesn't process DNS requests from users. The main router's DHCP advertises itself as the DNS server and clients of the dumb AP will use that to DNS directly from the main router.