They could start with not visiting a country their country invaded some years ago.

Although that's true, in that case I guess the issue is that exactly these tourists appear to be pro-war. For example, one Russian tourist said to a Georgian protester, "We are the Soviet Union. We are a single country".

I would bet any of the ones taking a cruise aren't using much (if any) of their resources to protest the war. Fuck them. If the bourgeoisie wants to be welcomed somewhere, they shouldn't let their nation become an enemy.

Do a lot of research beforehand. It's a massive region, with its parts being, well, very different from one another. Having at least some idea of what kind of experience you're looking for from your first visit is going to save you a lot of time and disappointment.

Also account for the massive distances - unless you have multiple consecutive weeks of free time and money to sponsor it, you probably won't be able to see it all in one trip.

I've been to Siberia a few times, mostly as a kid and then as a teenager, all in the same region, Tomsk and some neighboring cities - I loved it. While the cities and architecture may not be that different from other places, the nature sure does feel different from my home region, especially in terms of flora. Visiting it as someone who's never been to Russia, let alone anywhere in Siberia, is probably going to bring out even more differences.

The only caveat is, I don't know if it's a good idea for a foreigner to visit Russia right now. Foreigners have always attracted attention here, in both ways, so it's possible some people might get curios and inevitably try to discuss the war (or Ukraine, specifically, for that matter), which can relatively easily spiral out of control.

That being said, I'm sure there still are people still living in Russia that would be willing to accompany someone interested in visiting (and knowing English well enough, too).