I was in Crimea in 2006. Russian was the language. My understanding of the demographic trends was a 70/20 split between Russian/Ukrainians for a long time, which seems to be backed up by Wikipedia.

Prior to 2014, there was an influx of Crimean Tatars, returning from Siberia.

Since 2014, I heard there has been an exodus of Ukrainians from Crimea. But nothing I could confidently verify.

The Russians in Crimea were agitators for independence from Ukrainian rule. And they were happy with the Russian invasion. I wonder what their mindset is now, especially since many other Russians in Ukraine seem to prefer an independent Ukraine.