Is this big enough to produce a Tsunami? Apparently maybe only a small localised one, but I'm supposed to be getting the ferry from Lombok to Bali shortly and two of those have already burnt down the last 2 weeks!

A ferry in the open ocean is one of the safer places to be during a tsunami. Remember, it's not a surf-style wave, but a gradual increase in water level.

Indonesia's tsunami bulletins appear to be here:

https://rtsp.bmkg.go.id/publicbull.php

They've declared the event over - some waves were generated but nothing particularly large. Bulletin 3 for the recent quake includes wave height observations - maximum reported was 94cm; most were under 50cm.

I've seen "possible tsunami" pre-warnings, and a sea level gauge at/near Lembar showing sea level oscillations - so I would recommend keeping a close watch on some information source that's better than HN comment threads, yes.

I would upgrade the ferry and make sure to get a high quality one given all the swell in the ocean already (most of bali had 6ft+ waves yesterday) and this incident. Not worth the risk.

Tsunamis are only an issue close to shore. In the ocean it's barely a mild wave.

In a boat going further out is the safest thing you can do if there's a tsunami warning.

Easily big enough, but how deep it was generated and how the movements happened do impact the risk a lot.

Safe travels, friend.

the tsunami risk is negligible compared to the fire risk

Interesting times for the ferry indeed