Honestly bring up everything you think may be relevant. Did you use a certain system, software, or equipment, but only once or twice? I think you should still mention it, especially if it’s esoteric. You may be nearly equal to another candidate, but the fact you’ve even seen that thing may put you ahead. I prefaced with “honest” because overselling your actual experience or knowledge rarely ends well.
Mention any self study you’ve done, too, even if it hasn’t resulted in a degree or certification. Folks like to know you have interest in expanding your skills.
Apply for jobs even if the description seems only tenuously connected to what you’re looking for. I’ve seen some awful postings compared to what the actual work was going to be. It’s obnoxious and absurd that there’s such a disconnect, and ends up being extra work, but you may be surprised by what turns up.
They don’t have nearly as much of a problem as non-federated social media. The short answer is that it depends on how instances have things set up and how users decide to migrate- but still, compare that to non-federated social media where you’re just given the boot when things shut down