Is it possible to have one Craft install running Can a Craft install run on multiple domains and/or subdomains?

For example having the same Craft install running a blog Channel at blog.example.com and also an about Single at example.com
Sure it can. Craft 3 has multi-site support.
And for using a subdomain, you don't even need that, just point that subdomain at the correct template URL (eg. forward blog.example.com to example.com/blog).
The about single at example.com would just be your homepage.