I've been using hashtags on different platforms, and here's what I've observed:
Twitter: Trending hashtags are popular, but for my niche, they're overcrowded and don't help with views or engagement.
LinkedIn: Some hashtags seem to work, but not always for increasing post reach.
Facebook and Instagram: Some hashtags work here.
YouTube: Including the right hashtags is great for this platform; they really work for both shorts and long videos.