This is not entirely true. By the 18th Century (the time of the Chi'en Lung Emperor), the Russians had agricultural settlements along the Lena River all the way to Yakutsk. The growing season for the strains of rice that had been developed by the 18th Century is 90 days. And this agriculture was during the time of the Little Ice Age. Ninety days can mean more like 60 days if summer days are 20 to 23 hours long--and the temperature climbs toward 35 degrees Celsius, which in Siberia it does during the summer.
So all that would be needed would be for a Ch'ing Emperor, Dorgon, K'ang Hsi or Ch'en Lung, to decide that Russian barbarians to the North were more of a threat than a nuisance and decide to take over the Russian network of trading posts that by then had done the hard work of conquering Siberia most of the way to the Bering Strait. Maybe just to the Yensei River. Maybe all the way to Tobolsk, Tyumen and the Urals or even the Volga, depending on how far the Chinese decide to chase the Dzungars and Kazakhs. It would make for interesting timelines either way and result in a Siberia that is part of Zhonghuo all the way to the Bering Strait and the Arctic Ocean.