You don't believe one camp or the other. You look at how each camp reports on the same event. You use them against each other to get closer to the truth, like a trial where both sides argue their case and you are the judge.
So many times I've seen primary sources as reported by a user posting a video on Twitter, and later I'll read news coverage of that same type (from either side), and they'll omit essential pieces of information that don't fit their narrative, or include irrelevant information that pushes their narrative. The latter category is often an attempt to frame your thinking or make you think a certain way about a target.
To me that says that looking at the two different sides and judging their arguments to arrive at the truth works.
A final test would be to see if your arrived truth is close to reality, without relying on human observers. This is done by using your truth to make predictions and see if those predictions come tru. To see if your model of reality has predictive power.
Let's say you'll probably improve on the accuracy of your picture, if you take more different sides of the story into account.
For example: a hospital in gaza is bombed by israel forces. Hamas claims X number of civilian deaths and says nothing about terrorists existing in the building. IDF doesn't claim any number of civilian deaths but does say that, generally, terrorists hide in these hospitals. No one confirms basic facts like who are the people being targeted, were they actually killed, and how many innocent civilians were calculated as an acceptable loss to destroy the targets.
Overall I feel I'm left with even less information than when I started, since all either side can confirm is that Israel bombed a hospital. And this happens for a bunch of things: Israel bombs a neighborhood the UN has labeled a refugee camp. Hamas commits an act of terror with some number of hostages taken.
I cannot even confirm if the food, water, and fuel being sent humanitarian-ly to Gaza is enough for the population there. One side claims there is a huge crisis of resources, the other side claims there's no crisis whatsoever.
Lying is not only seen as morally justified but as your duty because your life and your compatriot's lives are on the line every second of every day of the conflict.