I don't really share my comic on social media, aside from a tumblr blog where I post character doodles and WIPs. In 2019 I deleted my twitter account. There's... a lot I have to say about twitter, but to keep things simple I felt worse every time I looked at it. I do have instagram and artstation, but I'm mainly posting stuff from my portfolio on there.
As far as promoting yourself without the main social media platforms goes, there's a few webcomic lists on tagpacker.com, and I also tend to share my work here on the forums if there's a topic that relates to something in my series. My comic ended up in the tapas daily snack a few years ago and I've seen a steady growth since then. Definitely participate in the forums if you see an interesting topic, the community on here is really nice!