The Chilean electoral system is really solid, one of the few things the entire country is proud of. Votes are counted publicly immediately after the election ends, results are done in a couple of hours, and are later ratified.
What is true is that Venezuela backed the riots the year before the election that Boric won. There was a video of some bitch from one of the Chilean lefty parties giving a speech in Venezuela, basically saying "we're doing it!". That election (and the first referendum about changing the constitution) was done essentially with a gun to the country's head: "vote for what the left wants or we continue burning and looting everything you've worked for". So people either abstained from voting (those two were voluntary) or capitulated and voted for the left.
As soon as the immediate threat passed, and the vote was made mandatory, the right came back in force, rejecting the New Constitution TWICE (the second one was drafted mainly by the right, but it was a win-win situation: "we want to keep the old constitution but if we can't, we'll get the new one we made").
So don't expect the reveal of fraud in the election, but there's already been discoveries about the funding of the riots (aside from that video, that can be considered a bint just talking shit).