Not familiar with carrd.co, but if they allow you to insert HTML, you can use njump widgets to display your long form nostr posts. It's only one line of code for each post.

https://m.primal.net/IGPV.png 

https://njump.me/about 

 This is great. Thanks! 

carrd.co allows you to create simple landing pages and basic websites with no code and for free or very low cost.

That's what I use for https://www.alejandrogil.net for example.