They all speak Russian. Lithuania has a sizable minority of Russian speakers, and has historical ties to Belarus. Latvia is predominantly Russian-speaking. Ukraine as well.
Knowing Belarusian, they can pick up Polish rather quickly.
As a last resort, Russia is still freer than Belarus politically and better off economically. Smolensk is half an hour drive from the Belarusian border.
This seems to imply the majority of residents of Latvia speak Russian natively. That might have been correct had the USSR existed a bit longer, but history took a different turn.
"Most Latvian businesses, especially in the Riga area, will happily serve you in Russian." That would be a more neutral and correct statement appropriate for this context.
Also relevant would be how Latvian government is publicly angling for Belarussian businesses willing to relocate to Latvia [1].
Regarding native tongues in Latvia... Currently, over 30% of Latvian residents speak Russian, Belarussian or Ukrainian natively, versus 62.3% Latvian. In Riga, the number of Russian, Belorussian or Ukrainian native speakers rises to over 43% [0] versus 47.1% Latvian.
[0] http://data.csb.gov.lv/pxweb/en/iedz/iedz__iedzrakst/IRG080....
[1] https://eng.lsm.lv/article/economy/business/belarusian-busin...
Still, even those statistics admit that Riga is mostly Russian-speaking [1]. This is where the IT crowd would land, anyway.
[1] https://www.csb.gov.lv/en/statistics/statistics-by-theme/pop...
In Latvia, especially Riga, Russian is spoken, but younger generations of ethnic Latvians are less and less welcoming of using it. Again, English is expected. There has been a distinct rise in shops in Riga where it's basically "Speak Latvian or English to me or GTFO".
Source: I'm a Russian speaker who visits all three Baltic countries at least 2-3 times a year, most recently last week.
My experience is anyone 30 or over speaks fluent Russian, but many of those will not admit to it - those in the 30-40 range are highly distrustful of anything Russian - and reasonably so given the history of the country. Anyone under 30 barely speaks Russian unless they themselves are immigrants from Russia.
I'd agree that in Lithuania a software engineering candidate that spoke Russian and not at least a "very good" standard of English or fluent Lithuanian would struggle to find work.
Lithuania is 5.8% Russian with 39% speaking it as a foreign language.
Numbers from Wikipedia.
That's an arguable statement. Russia is also ruled by lifetime president, any protests are being brutally oppressed, opposition leaders are being assassinated or imprisoned, state TV airing anti-Western propaganda 24/7. Ukraine and Lithuania look much better choice by all measures.