It would make sense for them to build on top of lightning given the investment SqCrypto is putting into the LDK.

The million dollar homepage?

That's a pretty big milestone. I suppose it makes sense for such large nodes to maintain a large channel with high liquidity on either end.

I just deployed an Umbrel node, it was a great, and very simple experience.

It's reasonably easy to dive in and interface with lnd directly if you want to get a peek under the hood.