I use the UniFFI Kotlin bindings, and when I analyze my APK, I can see that libmdk_uniffi.so file uses 6.3MB (plus another 5.2MB for armv7. This is the largest library in my app). Other libraries like rust-nostr use configuration code like this to optimize space:

[profile.release]
opt-level = 'z'     # Optimize for size
lto = true          # Enable Link Time Optimization
codegen-units = 1   # Reduce the number of codegen units to increase optimizations
panic = "abort"     # Abort on panic
strip = true        # Full strip the binary. A debug binary will be used for generating UniFFI foreign languages!

(copied directly from rust-nostr)

I don't know how much something like this would help, but the smaller the better!