Have you ever had a YouTube channel ?

I post unlisted (not public) vids on a YouTube channel occasionally, have embedded a couple of them here on occasion ... I haven't done anything more remarkable than that, but the main gist is that creating a YouTube channel is a piece of cake and good place to host videos for free for the foreseeable future

That being said, my experience is with video, I don't recall ever trying to convert an audio file to an mp4 with some image as a thumbnail (I'm guessing I could do this in a terminal with ffmpeg), and I think just a pure audio file would get rejected by the upload mechanism, so you may need to experiment with ways to add a token "video" track (even just a static image) to a purely audio file if you don't want to record actual video of yourself (or you could record video and just point the camera at a wall or something if you're not brave enough to be directly on camera ... but that's the simplest way to produce something the upload mechanism won't reject, as YouTube is oriented around video files rather than audio files)

On YouTube some settings can be saved for all future uploads, but not all settings, which is annoying, but after you do one or two you get the general hang of it, and you can go back later and change settings on existing uploads (like, say, disallowing comments or embedding) if you forgot to when initially uploading

If you have a Google account in any way (e.g., Gmail), I imagine you probably already have a default YouTube channel now but may need to finish setting it up, it's been a long time since I created any new Google account

Soundcloud might be an option for purely audio files but I don't know what they allow you to do just on a free tier