Don't know the context for that snippet you're sharing, but the issue for OSC 52 support for clipboard syncing is marked as `Open` in the Mosh repo https://github.com/mobile-shell/mosh/issues/637

To be fair I haven't tested mosh without tmux, I always have tmux running. So I guess the situation is that it's possible to make it work with tmux, but maybe mosh on its own doesn't support OSC52. Which for me is good enough.