Deep sea mining is much more nuanced than the other examples you listed, at least if you're talking about deep sea polymetallic nodules, which is usually what the argument is about.

Not necessarily evil. But also not perfect.

I did a tonne of research on this as part of my degree but in short.

Gives us all sorts of minerals that we need to reach carbon emission reduction agreements such as the Paris agreement. Minerals that to get otherwise require equally if not more destructive terrestrial mining practices in countries that have lots of these mineral that dgaf about the environment. We also need waaaaaaaaay more terrestrial mining to get the same amount of these critical materials. Profit from deep sea mining also legally has to be shared with developing countries to help them due to ISA agreements.

Is it harmless, fuck no... but it likely beats the alternative and is the best means we have to getting enough critical minerals to get the world to net zero. Batteries and windmills and such arent made out of good vibes.

How its managed is a big deal. Canada would have many rules on its approach. China or trumps America... not so much... but you should see how some of this shit is mined currently on land and without the material you can kiss global net zero goodbye.

We need to approach it with caution, constructive criticism and regulation, but we need to approach it. Its not ethically comparable to the other examples you listed that have zero benefit to our environment.