I don't know if this type of questions is allowed or not here, but I'll ask anyway. My question is that how should we, common people who haven't studied History academically in college or university, research about a certain historical topic on the internet or offline? (internet is preferred) Whenever I want to know about something historical, I am always bombarded with comments about how the info I know is 'X propaganda'.
Say Soviet Union history. People who say that Lenin and Stalin were great rulers who made a strong economy are called 'Left wing propaganda'. People who say that Lenin and Stalin were dictators who had a really poor economy are called 'Right wing propaganda'.
When I want to search something about India, people say don't listen to that, don't read this, etc. Some people online accuse India to have altered the history to cater to Hindutva propaganda. Hindutva retaliates by saying that it is all just 'western' bs, that they always try to make ancient India look bad, that western people don't understand ancient Vedic scriptures, history, etc and that all their books are biased.
I feel really confused about how to read about History and where to read it from. Everything seems like someone's propaganda.
The reason people accuse "history" of being propaganda is because history is important. People base claims to their identities, their nations, their actions, their morality, and so on, on historical claims. So it is going to be as complicated and fraught as any topic with real "stakes" associated with it.
As for how to go about it as a non-expert: you really have to rely on the community of other experts, the same as you would for claims about medicine, science, or anything else. If you're asking, "how do I know if X is a quality source?," there are several things that can help:
Is it peer-reviewed? That is, has the work been vetted by other experts?
Does it follow proper scholarly procedures? That is, does it cite its evidence, and cite the work of other scholars?
Who is the author? Are they a professional historian, or a political pundit? Where do they work?
How have others regarded this work or claim? That is, can you find reviews of the book by other scholars?
No single one of the above actually tells you if a source or claim is good or bad. There is non-peer-reviewed work that is solid. There is work by non-scholars that is solid. There are peer-reviewed, scholarly works that are trash. Citations can be very misleading. Book reviews can contradict one another, and so on.
So what's this mean for you? It means: there isn't some simple gold-star "this is the correct story" in history. That's the case even if you are only talking about academic history. To use your example: were Lenin and Stalin "great rulers" or "dictators"? (or both?) You can find positions within the academy that will argue both. Scholars disagree with one another, too. The above considerations are useful heuristics to weed out absolute cranks and grifters from the scholars, but they aren't perfect.
Which gets to a bigger and more tricky point: history isn't some static list of facts. There are some facts. There are positions that are better supported by evidence than others. But there is also room for contestation, interpretation, and revision. This is what professional historians do.
Another way to put this is: if someone is telling you that there is one and only one way to interpret the past, be suspicious. If it seems too clean and simple to be realistic in our crazy complex world, be suspicious. If an author can't say, "some people understand this as X, some people understand this as Y, I lean towards Z," beware of their lack of nuance. And, most of all, beware of anyone who claims that every position contrary to their own is "bias" — that by itself is a sign that someone is trying to sell you something, and that's not what the serious study of history is about.
There are resources, like /r/AskHistorians and its book list, that try to point people towards sources that experts think are good places to learn about a topic. There is, of course, always room for criticism and debate of such recommendations; real scholars welcome that, and don't try to just shut it down. Most importantly, to understand history well you must read somewhat widely in it — a single book or author is rarely enough.