It's hard from a Tweet to fact check that claim that Ukraine interfered with the 2016 election. Clearly Mueller and the FBI found nothing about such interference.
I don't think the Mueller investigation was even looking into that, were they? Ukraine's not some nuclear superpower, and if people in some country that's considered a small player on the world stage are "outed" (or just reported, whatever) in the media like that for wanting one party or candidate to win over another, I don't see why that would be even be worthy of investigation.
And it's not shady, sketchy, or suspicious that Ukrainians would have felt strongly that Trump was a threat to their country and thus some of them would have done whatever they did - which appears to be limited to alerting the FBI of Manafort's work there, which, iirc, resulted in Manafort being correctly charged with a violation of a "unregistered foreign agent" law.
This was all very "out in the open" dealings at the time, reported in the widely read magazine FP, and was considered a total non-issue by republicans and democrats alike before right now. The Republicans might try to "throw shade" at the evidence the Ukranians gave the FBI (a ledger with Manafort's name on it in multiple places, iirc) but that's not going to go anywhere. "Using the Trump impeachment to actually exonerate Manafort" would probably not be a wise strategy for them to pursue beyond making conspiratorial-sounding implications. So, they're just going to keep trying to make Ukraine (and somehow thus Biden) look just fishy enough to where they hope it justifies in the mind of some skeptical republicans the "missiles-for-antiBiden headlines" deal as "legit foreign policy," and not the bribe/foreign contributions ban violation it is.
That's not a problem for people looking at the evidence and Trumpers aren't looking no matter what. The evidence is there in multiple sources beyond the phone call.
Nothing is going to change the dishonest Trumper talking points. Other than not feeding into them and repeating them, what else should people do?
Good question, and I have no idea. The real "audience" here with this is small, (whoever those people in said audience are, which is not immediately obvious. Senate Republicans with a conscience, if they exist? The SCOTUS itself, etc?)
If this the Republicans' best stuff (and I think it might be) then I personally am enthusiastic about the upcoming debates I'll engage in, with "regular voters who are, or are potential impeachment agnostics" being my own intended audience, be they lurkers or active participants in discussion.