I once tried to do Let's Encrypt or any free SSL with my namecheap domain and apparently you can't. Is that true? I don't really want to change domain name companies because I'm lazy and it's probably time consuming to get right... can I get free HTTPS if I host my site on Netlify and just point my URL there?
All I use it for is my Jekyll-powered personal site on GitHub pages. I don't mind not using GitHub for it anymore, just want it to work with SSL.
In order to do this, you'd need to put an SSL endpoint between your github page and the client. It could probably be done but it sounds like a no-no.
For instance, I'll bet that if you set it up so that your namecheap DNS A entry was pointed to your own box that had nginx/haproxy/cloudflare/whatever handling SSL decryption (and certs) and then backended to your github pages, it would work, but I'm not a fan of the idea.
GitHub doesn't support custom SSL for pages. A workaround is to change your DNS provider (which is probably Namecheap right now) to Cloudflare and use Cloudflare's free SSL (so it essentially will be an SSL proxy).
You can do this wile still maintaining Namecheap as your registrar, and it's totally free.
Domain registrar has nothing to do with the hosting. As long as you can point a domain to an IP address you can get a certificate.
Namecheap even goes a step further and has an API for domain validation (makes LE certificate authorization easier) so they are very friendly in regards to Let's Encrypt.
All I use it for is my Jekyll-powered personal site on GitHub pages. I don't mind not using GitHub for it anymore, just want it to work with SSL.