[thesuperbigfrog]

>> I've been programming on my phone with termux + vim. It's been sort of a delight.

Seconded.

With Termux (https://termux.dev/en/) I have C, C++, Rust, Go, Perl, Python, Ruby, and more in my pocket.

The screen is small, but the tools are mostly the same you would find on your favorite *nix box.

No network connection needed beyond getting the packages you want installed.