Haven't tried iroh-ssh but since Synchi just uses standard SSH under the hood, it should work transparently with any ProxyCommand setup. Cool project, though!

Many sync tools like rsync are actually one-way (yes, only a mirror/backup). Two-way means changes on either side get synced to the other (Synchi helps you resolve conflicts). That said, Synchi can also do one-way mirroring if you set force=root_a in the config.

If you wish to sync between computer and Android, you don't even need to install it on your phone. All you need is setup ssh connection and storage permission inside Termux terminal. I have written a short tutorial here: https://jakobkreft.github.io/synchi/termux.html if you wish still wish to run Synchi directly from Android, to sync between two android devices for example you can install it from source like this inside Termux terminal:

pkg install rust git

cargo install --git https://github.com/jakobkreft/synchi

Then add cargo bin to your PATH:

echo 'export PATH="$PATH:/data/data/com.termux/files/home/.cargo/bin"' >> ~/.bashrc

source ~/.bashrc

After that you can just run synchi.