The only Russian app I'm aware of is Telegram. What other Russian apps might people be unwittingly running?

No servers in Russia. Given Pavel's prior history it seems unlikely that he would cooperate with Russian government. Plenty of other criticism of telegram is warranted but it's probably not a tool of the Russian government.

Edit: related https://hate.tg/

I would argue that Telegram is a much, much larger security threat to the average individual American than Tiktok. Except they comply with government search warrants and don't enable E2E encryption by default so they are useful to the American National Security Establishment and get to stay.