There are subreddits for comics like r/webcomics, r/comics, and r/webtoons and some others, but I haven't heard much of downvote bombing yet.
r/comic and r/webcomics are more for one off gag comics, but people do post long running stories there as bits and pieces, with a link to the rest in the comments.
r/webtoons is more of a discussion forum for loved and hated webtoons. People do share their work and ask for feedback & advice there too. But you're only allowed to promote on weekends or if you're looking for specific advice(character design, covers, logos, etc)
I haven't posted to the comic subreddits since I don't have a comic to share yet. The only places I have mild success is magicalgirls, clipstudio, copic, and furry. Pretty much any subreddit specific to the topic you're drawing.
I know r/artistlounge gets a lot of posts of people frustrated with social media. Most common piece of advice they get is to network in real life, but that's something I have yet to try.
I'm constantly bouncing back and forth with my motivation to draw, so I unfortunately can't lend any advice for that. I came back to insta after a year for MaydenDressUp, but I might leave again afterwards. I kinda felt happier just drawing with no audience, but that's just me... on a good day. I can't speak for others.