Is there any specific reason you recommend me c-lightning? Is it possibly simpler than LND? I'm a person who has not much free time these days and wants to experience with the lightning network whenever he finds some. I'd definitely want the most suitable or easiest to use.
C-lightning is less resource intensive and it's really easy to use, even if you want to try experimental features like dual-funding. I also like that you can easily open multiple channels in a single transaction. On the other hand, you will me missing out on stuff like Sphinx Chat, ThunderHub, Lightning Terminal, Zap Wallet and BlueWallet integration. You should make thorough research so that you don't blame yourself later.
Also, if I want to use c-lightning, why do I have to uninstall LND?
You don't have to, but you might not want to keep any unused packages related to it on your system.
Does that work only for US purchases?
Yes. See below.
Why did my purchase with a Moon Visa® Prepaid Card fail? [...] 4) The merchant may not be based in the US. Moon does not support payments to non-US based merchants.
Have we seen exchanges start adopting Lightning, instead of listing more “faster” shitcoins?
Yes.
https://github.com/theDavidCoen/LightningExchanges