It appears that cross-compiling with Rust is rather straightforward: just install the target you're… hmm, targeting with "rutsup target add <target>", and use "cargo build --target <target> --release" — not much harder than it is with Go.
Considering that your target is available via rustup — mine, PowerPC MUSL system wasn't and I had to build natively, I'll figure out how to add my own targets later. But building for my old ARM machine went without a hitch — and, surprisingly, the binary works😂

In case some of the crates use C code and build something themselves, like ring crate does, you have to point cargo to the right tools using the environment variables, but in a lot of cases it figures everything out on its own.
Also rust crate version 0.16 didn't support 32-bit PowerPC properly so to port TUI RSS reader here https://github.com/veeso/tuifeed I had to update a few dependencies to use newer ring 0.17

Some problems arise from software relying on atomics (thread-safe types) from the standard library, which aren't portable — luckily, there is portable-atomic crate: https://github.com/taiki-e/portable-atomic
Replacing atomics from standard library with the ones from portable-atomic IS straightforward, but in my case it was a dependency of a dependency using it, so building the RSS reader involved adding a [patch.crates-io] section to Cargo.toml to use a local patched version of crate.