Can you use Git Hub? yes.

GitHub is also an option you could pursue when moving to Git. GitHub has a lot of new features and offerings that Azure DevOps does not have. However, there is basically no documentation from MSFT on how to configure builds and various other automation options in GitHub. I'm sure it's possible but there will be a fair amount of guess work. Getting your pipelines fully converted to YAML will be the first step in making the transition to GitHub.

Community (Free)

I use GitHub to host all of my community projects which is great for that. I can share the code and anyone can pick it up and use it as they see fit. Private repos are now also an option. However, these still below to a named person so you'd want a service account or centrally managed account to create all projects.

Pro

For 4 USD a month, you can upgrade 1 account on GitHub to GitHub Pro, which gives you more stuff. Using YAML plus actions, you could probably get a lot of the same benefits from Azure DevOps without having to use DevOps. 

Thoughts

 I think the prospect of using Github for community or personal development for F&O is a good idea. Git is simple and so is GitHub. You can work and share your code with whomever you like. Additionally, private repos are now free so you can use those, too.

However, the prospect of using Github for an implementation or support project is a much harder sell for the client or organization. While I'm pretty sure you could use GitHub to get to around the same service level as Azure DevOps, there is a fair amount of risk. That risk is, in my opinion, simply too great to suggest using it for the time being. There is nearly no documentation on the subject and there is no one at MSFT you can call for help specific to F&O. Although it may look like Azure DevOps isn't the favorite for MSFT in terms of product hype or feature development, DevOps is still a proven tool we can rely on. I got the chart below from this site but I think it's really helpful given the context.