Perhaps youtube is not the best place for this kind of stuff. I would concentrate on forums/blogs such as these and other net places where olden computer enthusiasts gather and get their news from. There are still enthusiasts of TRS-80 for example Maybe it's also worth contacting outlets such as RetroGamer - if you haven't already.
I'm not a big fan of reddit in general but it did help with some of my obscure projects. The exposure is huge, problem is it's only for one hot minute, especially if the hivemind there doesn't like it for some reason.