I actually do use Rumble (there are some more controversial-but-also-left-leaning creators that got banned from YouTube that I like), but man the ads on there are insane.
COVID conspiracy theories, vaccine "alternatives", political ads for obscure Republican candidates, stuff like that. Fortunately, at least for now there's not a lot of ads (I suspect that they can't find a lot of mainstream advertisers), so generally I only got to watch one of those ads before the video starts.
I don't know - for example, here is a video of a couple of scientists who explain in detail how they have analyzed the vaccine contents and how authorities then have reacted to their complaints:
I made it clear that these were the ads, not the direct videos.
That said, the COVID vaccines are safe and saying otherwise is kind of intellectually dishonest. Just because you can find one video where they "analyzed the vaccine contents" doesn't discount all the research and sampling data that has been taken.
If you haven't gotten the COVID vaccine, you probably should.