[orthoxerox]

There are still enough people speaking Ukrainian even if we roll back the clock to 2019.

  Lviv = 2.5m
  Vinnytsia = 1.5m
  Ivano-Frankivsk = 1.3m
  Khmelnytskyi = 1.2m
  Rivne = 1.1m
  Ternopil = 1m
  Volyn = 1m
  Chernivtsi = 0.8m
  Zakarpattia = 0.8m (I've subtracted the Hungarians)

That's 11.2 million Western Ukrainians, who are overwhelmingly Ukrophone. Even if you completely ignore the rest of the country (which definitely wasn't completely Russophone and is even less now), that's still more than the number of Czech speakers.

[egorfine]

Well, yeah, that sounds plausible. It's in the same ballpark as Czech, and which language is more popular is largely irrelevant when they are that close in numbers.

Whether the numbers are correct is debatable but we have no way of checking that.