I must say: this is a great question! This is my personal take on things.
I’ve pinged @ei8fdb but haven’t got a reply. Is it rude to call this out (like I am now)?
Yes! I never do it. The reason being that in FOSS we are all volunteers, so there is no case for demanding (or even expecting) a reply. I always assume people want to reply to me, but something more urgent is getting on the way (work, life, that kind of thing). I have adjusted my expectations to not expect a reply. If it comes, then great. If it doesn’t, well, that’s expected, so no issues.
If you reach out to someone and don’t hear a reply, what is the right thing to do in this community?
In any FOSS community, I either ask someone else, or I take action myself if applicable. For instance, if I asked about doing something and nobody replies saying yes or nay, I go ahead and do it. I assume that, if someone were strongly against, they would have said something. If I was asking for information, I look for an alternative source.