Welcome to Nostr!

Damus is just one app that is built on top of the Nostr protocol. There are all sorts of other apps that are also built on top of Nostr, and because they all "speak Nostr," they are interoperable. Sounds like you are on iOS, so you could also check out Nostur or YakiHonne, which are both apps like Damus that you can log into with your same Nostr credentials (keys) and all of your notes and follows will just show up in those apps, too.

Now... You mentioned something about your Cashapp Lightning address not working. I don't see your Lightning address in your profile, so where were you putting it in?

Your Lightning address is for RECEIVING zaps, and you have to go to your profile and add it there. Damus should have a field in your profile specifically for your Lightning address.

If you want to SEND zaps, you will need what is called a Nostr Wallet Connect connection string. I actually just finished up an article talking about how this works that you can go read at www.nostr-reviews.com

Cashapp likely does not yet support Nostr Wallet Connect. You will need to get a Lightning wallet that does. My recommendation would be nostr:npub1h2qfjpnxau9k7ja9qkf50043xfpfy8j5v60xsqryef64y44puwnq28w8ch.

In addition to this, because Apple is dumb, you will need to activate the ability to zap other users' posts by going to https://zap.army.