Greetings,
I am experiencing the same issue. After banging various ways to figure what's wrong with my OpenWRT came to the forum for help, but happily this thread has already started. I am on the same hardware as the OP (Archer 7 v2), running 19.07.3, and getting
Cannot install package
errors when trying to install curl, or a libustream library. Those don't even show as being available by "opkg list". It all started with my trying to install SSL for DDNS update requests.
Hopefully top men are looking into fixing the package sources. Much appreciated!
Cheers,
tjk 