There’s some debate on how you define a true L2, but I’d say Lightning is the only one that really qualifies. All the rest have very different trust tradeoffs.

Stacks is an affinity scam as far as I can tell.

Ark is promising (still in development) and probably has the best trade offs.

I also think Alpen (from Alpen Labs) and Spark (from Lightspark) are interesting.

Cashu is e-cash reinvented. It goes way back as pretty much being the OG cryptosystem back in the 80s made by David Chaum. @npub12rv5lskctqxxs2c8rf2zlzc7xx3qpvzs3w4etgemauy9thegr43sf485vg is the resident master of e-cash here and is a lot more familiar with it but it's essentially an off-chain way to on-ramp/off-ramp/utilize the Bitcoin system.

Basically it translates bitcoin into tokens that exist on your device that you can use in apps - almost like an an arcade where you can get your money back for the unspent bitcoin you've used.

Cashu/nostr wallet has been the only system I've found that allows the best possible UX for most users, who are largely untechnical - simply scan a QR code or use the receiver address generated with Cash App (used by ~60 million young Americans) and you can pretty much create bitcoin experiences seamlessly.

if you wanna give it a spin to experience the magic, try it out here https://robotsbuildingeducation.com

E-cash wiki

https://en.wikipedia.org/wiki/Ecash

play with cashu.me and throw sats in there.