Display a list of all public questions and posts to a community user, regardless of whether or not that user is subscribed to the groups or users who posted.
What we've tried
SOQL query on feed items, then filtered after the SOQL for just that community because the where filter on networkId is broken (known issue).
We have so many feed items that the SOQL is now non-selective, which is breaking tests on the deploy, but not actually breaking anything in production. We are working on making it selective but that's not working.
How about the ConnectApi you say?
The ConnectApi has a getFeedElementsFromFeed method but the Company FeedType is not supported in Communities. That FeedType is the only FeedType that would return as broad of a scope to include questions and posts to which the user isn't following/subscribed but is still public and can see.
Aside from trying to make the SOQL selective, is there some other solution that I'm missing?