GitHub Discussions vs Slack for community

Im thinking about an alternative to running a Slack group for product support, mostly because of the 90 day limit on content.

I used to use spectrum.chat which was great, well-indexed, lots of design communities, then MS bought it and killed it, so it now redirects to https://github.com/features/discussions/

But, despite my whining about that a few times over the last couple of years, seems that GitHub Discussions is freely available and they also have a top-level Organisation Discussions option.

It seems Discussions is only searchable within GitHub, which is a minor disadvantage from a marketing aspect. It will also require people to be able to login to GitHub to be able to post.

The other alternative I've considered is reddit