I think it's often the case that neither A nor B are true. Common opinions are shallow, often simplified and exaggerated or even entirely besides the point.
Now, you're asking what a good way to form opinions is, well, it depends on what you want.
Do you want to know which side you should vote for to bring the future towards the state that you want?
Do you want to figure out which side is the most correct?
Do you want to figure out the actual truth behind the political issue?
Do you want to hold an opinion which won't disrupt your social life too much or make you unpopular?
I expect that these four will bring you to different answers.
(While I think I understand the problem well, I can't promise that I have a good solution. Besides, it's subjective. Since the topic is controversial, any answer I give will be influenced by the very biases that we're potentially interested in avoiding)
By the way, personally, I don't care much what foreign actors (or team A and B) have to say about anything, so it's not a factor which makes a difference to me.
Edit: I should probably have submitted this as a comment and not an answer. Oh well, I will think up an answer if you respond.
It seems to me that you might not have read the question/premise carefully. If you did and stand by this answer/comment, let me know and I'll respond when I have time
There are also times where "foreign actors" (I assume by that term you mean actors interested in muddying the waters in general, not just literal foreign election interference) know that it's impossible to push a conversation towards their preferred 1)A or 5)B, at least among informed/educated voices, so they try to muddy the waters and push things towards 3). Climate change[1] and covid vaccines are two examples that comes to mind.
Though the correct answer for climate change is closer to 2) than 1)
I actually just meant sowing discord by pushing half the population towards one and the other half towards the other in cases where it doesn't really affect them, but that's a good point. It's important to not be deceived into thinking issues are complicated when they are really not.
Take a random political issue with two sides A and B. Suppose that exactly one of the following would be true for me given my moral framework and unlimited time to process all public information about the issue:
Let's also say that:
The major issue to me here is (1), which might only get worse over time. I am aware of the post on epistemic learned helplessness by Scott Alexander, but I have become a little wary of certain academic fields. I have generally liked using Wikipedia to quickly explore issues, even though there are occasional biases (which have hurt this website in the past). I have also enjoyed reading blogs and opinions from people who appear highly educated and intelligent, but there are natural biases there as well.