Here is the home for all that is MiSTer FPGA. Tons of developers and enthusiasts can be found here, talking about the all the nuances of the platform, including cores in development, framework changes, and ideas for new features. In addition you can find game challenges and other fun community events.
For people who need additional assistance getting started, or people who want to dial down on getting their display settings just right, this is the place to find help.
Channels exist for working with developers to drill down on any bugs and inaccuracies or discuss new features as well, so join the community today!