While there are additional Layer 2 bitcoin blockchain technologies, this "Layer 2 Roundup" focuses solely on Lightning network ⚡ and Liquid Network 🌊.

Here's from a Tweet that describes this.  It is not fully comprehensive, but places most of those I've heard of.

> L1:
> Most sercured monetary network ever existed.
> Segwit, Taproot
>
> L2: 
> Payment Network: Lightning
> Tokens & NFTs: Liquid
> Smart Contracts: RSK, Stacks, Sovryn

https://twitter.com/greek_prick/status/1472078747880894466

cointastical

Viewing the thread on Blockstream's Mastodon account is a pretty decent method to read it as well:

https://bitcoinhackers.org/@Blockstream/107741222478465210 