the mosh.org homepage links to this extension for Chrome/ChromeOS:
https://chrome.google.com/webstore/detail/mosh/ooiklbnjmhbcgemelgfhaeaocllobloj

that used to work when Chrome supported NaCl, but unfortunately, it dropped support completely a few years ago.

the Secure Shell extension now includes a WASM port of mosh and thus works on all Chrome platforms again:
https://chromewebstore.google.com/detail/iodihamcpbpeioajjeobimgagajmlibd