(This is not an argument against anonymity; I don't need to know where these accounts really live. I do need to know where political advertising is funded from, because there are laws about that.)
While I don't claim to have researched this issue in depth and it's worth taking this with a pinch of salt, I'm yet to see any evidence of this, nor has it been a part of most of the leftist reporting I've seen. The only instance I've heard of where a specific Twitter account has been accused of being a Russian misrepresenting their nationality was ian56789, and that accusation was false, as he demonstrated by going on Sky News and giving an interview.
There's really two parts to the populist wave: "establishment politics isn't delivering what we need" and "we must turn to what seems like a Man of the People". The first has some extremely valid points, the second has (mostly) been a total disaster.
Enabling horizontal communication, not controlled by the Mainstream Mass Media.
Advocating for outright bans on voicing disfavoured viewpoints is so obviously illiberal and thuggish as to be politically unpopular, which is why it is always platforms targeted rather than individual speakers, and why there is always some rationalisation for the complaint other than the viewpoint being expressed (Russian bots! Fake news! Algorithms optimising for rage! Harassment!) but in the end the root cause of the complaint is always that someone said something that progressives didn't like.