you could comb through opencv source (git blame on specific files) and track down those people that wrote about it. the tutorial I saw mentions opencv v3.0.0, which makes me think it has aged several years without anyone touching it.
“build from source” must mean cross-compiling in this case. be sure you’re actually executing the toolchain/compiler for android/NDK (not anything for the host), and that all the flags make sense (it’ll need to know what architecture and whatnot). cross-compiling is more finnicky than just building for the same host.