Unless there is no Russia as we know it, chances are that Russia will be successful in gaining control over Siberia and North Asia. The potential economic benefit of potential mineral wealth, fur trade, and a land border with China are too appealing to pass up.
Let’s put things into the historic perspective. Initial exploitation of Siberia’s
mineral wealth is an issue of the XVIII and on a large scale did not pick up until well into the XIX with most of it happening only in the Soviet times. Even in the early XVIII it was too late to talk about not going to Siberia so the mineral wealth was not a factor.
Trade with China on more or less serious level started in the late XVII (Nerchinsk Treaty) and was not a factor in the early colonization.
On the initial stage the driving factor were predominantly furs. But as early as at the time of the first Romanov tsars the furs were far from being the Tsardom’s top export item. Leather, flax, hemp, fat had been higher on the list. Which, of course, does not mean that the furs were not important.
If Russia were more involved in Europe, there might not be the need for it. But given the general attitudes of the Russian ruling class, expanding eastwards with small opposition versus permanent entanglements in Europe, they will choose Siberia pretty much always.
At least in OTL the Russian ruling class had a very limited interest in Siberia except for the very few well-connected individuals who could get the gubernatorial positions. For the rest it would be a rather unpleasant semi-exile. If you include Ural into “Siberia” then the list of the interested individuals will expand but this applies to the XVIII and later and, again, you are talking about only few well-connected people capable of getting the concessions on the local state mines and metallurgical plants and later to be bailed out when they made them unprofitable (which was usually the case). The nobility in general was not benefitting in any way and there was no noticeable serfdom-based expansion East of Ural. At least in OTL the process (post Yermak) was state-driven and the Cossacks involved usually had been on the state service.
Now if Russia doesn't exist as a state, and in that case I also count personal union scenarios with (Poland-)Lithuania or Sweden, or if the old domains of the Kievan Rus remain divided, then a conquest of Siberia would likely not be a priority. A Swedish-Russian union would be wary of Russia stumbling its way into clear superiority over Sweden, for example.
At the time Swedish-Russian union became a realistic possibility (ToT, younger brother of GA) conquest of Siberia already started and IMO superiority consideration does not look very convincing: Swedish-Russian or Polish-Russian monarch would be interested in income and the furs were as good source as any.
But this conquest never was a priority in the Russian policy: Russia was expanding into a power vacuum stopping at each and every obstacle (Dzungars, Manchu) and moving forward when it either disappeared or weakened beyond any reasonable doubt. Even in the 1850 most of the cabinet was against expansion to the Amur and Pacific and this was a local initiative in which success justified violation of the explicit orders.
Comparing to the resources spent upon conquest of the Caucasus or even the CA those dedicated to the
geographic Siberia were minuscule and n the extended meaning of the term (including Russian Pacific) the intensive process started only in the late XIX.
Now regarding who could have conquered it instead, the UK, and the Scandinavians are obvious possibilities. The Dutch potentially, too. They were very involved with Arctic exploration early on and I could see an arrangement similar to the French rule over New France in North America working out (as in limited urban settlements along access points, e.g. rivers or coastlines with extensive trade networks with indigenous groups). That colonial style of governance only requires a decent navy but not too many settlers, and given the climate and the distance of Siberia to the rest of Europe, there likely wouldn't be any widespread settler colonialism.
Most probably. The open question is would it be sustainable at all with the naval access available only few months per year and no way to sustain the colony by the local resources.
Another thing to consider is of course China. If Russia doesn't expand eastwards, China will be very interested in seeing no hostile nomadic entities emerging in the area (s. the Mongols, Manchus, Kazakhs). But I think it's unlikely that a pre-industrial China would care to expand much further north than Outer Manchuria and the southern shore of Lake Baikal.
Indeed. China could (and did) claim the wast territories which it never controlled in practical terms. This would fit ideology by which everybody was a vassal of the Emperor of China. But even the area on the left bank of the Amur was mostly out of its control. It seems that the Chinese started moving into the Russian Pacific region only after it became Russian and on the Amur there were few settlements along its left bank but pretty much nothing further north.
The same applies to Japan to a lesser extent. They would probably be open to colonizing Kamchatka and the Russian Far East in general, but wouldn't be too willing to expand into the interior due being unable to easily project power beyond Lake Baikal.
Which period are you talking about?
