For my experience:
Facebook - mainly promotion is done through groups if you can find the right audience
Reddit - just like the above. I believe it much affective as I able to gain 200 views alone from it
TikTok - no idea. I might try to get into it as a lot of people mentioning about it
Instagram - unless you have a huge follower and have close connection with them (not just stranger), it won't help much. It like out of those 100 followers, only like 10 - 20 people might watch your videos