You can follow the submissions via an RSS feed.

For example, if you use the link Https://lemm.ee/feeds/u/Corr.xml?sort=New, all your previous posts will be displayed.

Instead of lemm.ee you need to specify the instance where the user in question is registered. And instead of Corr you have to enter the username. For example https://discuss.tchncs.de/feeds/u/fryboyter.xml?sort=New. That would be in this case my contributions.

Mainstream? Not a chance. Many people know Twitter and Facebook, but they don’t know what Lemmy or Reddit is, for example, and therefore don’t use it.

And it usually doesn’t matter if solution A is better than solution B. What becomes mainstream and what doesn’t usually depends on other things.