As someone who hasn't been watching closely for a while, any thoughts on which of those seem most interesting?

To me Mina and Zcash are interesting since they (plan to) use cryptographic arguments to show that chain states are valid, which leads to some nice features, such as better light clients. I'm probably biased since our own startup was influenced by them. Besides that, I'd say NEAR since it seems like the most promising sharded chain that's in or close to production.

(They weren't on the list since Mina hasn't launched quite yet, Zcash isn't PoS though it might switch, and NEAR isn't PoS in its current form, but will be soon.)

All of those are run by a singular entity. This makes it trivial for them to implement PoS.

That's not the use case something like Bitcoin is built for.

That's flatly untrue.

How can that be controversial? They all had an ICO to begin with. Some of them have even registered a company or organization to back it up.

The controversy is in the language "started" vs. "run."

Tezos, as an example, is governed by voting and on-chain governance. It isn't "run by a single entity."

Ripple or Tether are, though, sure.

Governance is more than a voting protocol. Tezos is not governed by equal actors.

There is a "Tezos Foundation". They control 30% of all staked XTZ. They checkpoint the blockchain regularly to provide correct history.

It seems to me that admin rights to the bitcoin core github repo count for a lot more than a 30% vote.