On May 1, 2018, GitHub changed the suggested IP addresses to put on the A records for domains that use GitHub Pages. The new ones now support HTTPS for custom domains, but the old ones did not. Here are the old ones for historical purposes:
- 192.30.252.153
- 192.30.252.154
Here are the new ones:
- 185.199.108.153
- 185.199.109.153
- 185.199.110.153
- 185.199.111.153
and, thanks again! even years later, this info was critical...