It is Latvian. It's also Russian. It's also Singaporean. It just depends on who you ask and how much you want to look into it.

But yeah, that's a large part of why I use Collabora instead of OnlyOffice, it's just a lot less sketchy.

Yes, there is evidence. Did you read the linked post?

I wouldn't have any problems with it if it were just free open source software. But they also offer paid services. Internationally they do that through their Latvian based subsidiary, obfuscating their origin. At home in Russia their suite is renamed R7-Office, which is a reference to the first ICBM with a nuclear warhead. The release imagery also depicts the release of a rocket that looks like the R-7.

Altogether pretty sus, if you ask me.