Here's some actionable advice. Go to your local president / prime minister. Preferably a populist. Tell them how you see the dominance of a few megacorps as a threat to national security. This argument is especially strong if from your point of view they are foreign megacorps. Throw in something about colonialism if it would help your case. Express your wish that they do something.
This is seems like a good advice to increase competition by using nationalist sentiments. The problem is that many of these nationalist countries would outright ban competition. So people who demanded local alternative will end up with less competition.
