You could substitute Jekyll for other supported frameworks.
Pros:
* Markdown (so super flexible)
* Git as the backbone (free CRM, free history)
* Customisable (if you know how to code)
* Free templates
Cons:
* Jekyll is a bit of a pain on Windows but should be fine on Linux/Mac
* Images might not load super quick from GitHub's servers
* You need to know basic Git
Microsoft famously tried to outcompete the Internet via their existing monopoly on Windows with MSN (not just the messenger) back in the day, and have always been super hostile to free-software. They have also, like any corporation, stopped to maintain several services over the years and the fact that beyond their public image they don't have any incentive to keep Github Pages going doesn't inspire me confidence.
The fact that Github Pages were up and running before Microsoft's acquisition of Github is a reason to be worried. There's no money flowing in from that service and it probably costs a fair amount. Despite their "we love open source" statements, i've yet to see Microsoft open-sourcing any significant product (including Github) and specifying/standardizing existing stuff like Github Actions.
Microsoft is still a strong force for evil in this day and age. I only wish they were disbanded during the antitrust investigations of the 90s instead of putting Apple on life-support: the world of computing would be such a better place without both Apple and Microsoft to shit their monopoly on our faces.