>How much does one channel open take then?

3 block confirmations. Some other solutions offer even 0conf (Phoenix, Blixt).

>How heavy is that type of TX with minimum numbers of inputs?

Here you can calculate yourself: https://coinb.in/#fees

>I know that there are solutions with custody trade-offs too.

I think you don't know about many self-custody LN nodes, here are explained:
- https://darthcoin.substack.com/p/lightning-wallets-comparison
- https://darthcoin.substack.com/p/private-lightning-nodes
- https://darthcoin.substack.com/p/getting-started-ln

DarthCoin

bitcoin

How many ⚡ channels could we open in a single block?

bitcoinbumbleB

Thanks!

How much does one channel open take then? How heavy is that type of TX with minimum numbers of inputs?

In terms of scaling, I'm just interested in sovereign use. I know that there are solutions with custody trade-offs too.