It may not be apparent to many users that the various channel owners create, submit to Roku, and maintain the specific Roku-compatible versions of their apps that run on the Roku operating system. They also specify the geographical regions in which their channel apps nay be offered. Roku just provides the platform on which they run.
If you want to have a specific channel for your Roku and region, you need to convince the channel owner to create a Roku-compatible version of their app, specify where it is to be available, agree to Roku's conditions, and submit it to Roku.
Great American Family doesn't have a standalone channel/app yet available, but you can watch it on some other "cable-alternative" streaming services as part of their package plan.
https://www.greatamericanfamily.com/faq/
----
FrndlyTV was one of the first to carry it, but from the above link, seems to have expanded to some others. (Frndly TV, Fubo TV, Philo, Hulu, DirecTV Stream and Sling TV)
https://channelstore.roku.com/details/300d1f91b5e583145c8a3fba6f08dafd/frndly-tv
https://try.frndlytv.com/ (Frndly website - channel list)