We know there was an informant in the Trump campaign.
As there should have been.
Just to be clear, we do NOT know that there was an "informant" in the Trump campaign. We do know that many campaign staffers and associates were blatantly violating campaign laws, including in some cases in ways so criminal they are currently in prison, and that the FBI has been investigating these crimes since roughly the time he won the primary. Others have agreed to testify against the campaign in exchange for reduced sentences (e.g. Flynn, Papadopolous, Gates, Pinedo, Zwaan). All of those people provided "information" to the FBI about ongoing criminal activities. That does not make them "informants".
Other people have released supposedly confidential information about the campaign but have not been charged with crimes (Steve Bannon, Roger Stone, etc.) and they are not informants either. They are all staunch Trump supporters to this day.
Trump's conspiracy seems to suggest that the FBI or other federal law enforcement agency planted a law enforcement officer within the Trump campaign for the purpose of discerning criminal activity, but this is a somewhat nebulous charge when you're talking about a campaign that willingly and gleefully accepted FBI security details for multiple persons (because it is flattering). ALL of those FBI agents were looking for criminal activity, that's their job. That doesn't make them spies, that makes the FBI agents. Invited FBI agents. If a presidential candidate who is under FBI protection commits a crime in front of an FBI agent, that agent is of course going to report the crime he saw. He would be negligent not to. That still doesn't make him an informant.
And in the current "campaign spy" conspiracy theory, classified briefings on what really happened caused Democrats to say "Yep, the FBI sent agents to interview Trump campaign staffers involved in criminal activity" and Republicans to say "Uhhhhh, nothing to see here, move along..." If that isn't definitive resolution for you, what is?
So I don't know what Trump is really trying to say, and I suspect that he doesn't either. This whole thing reminds me of the time he said Ted Cruz's father assassinated Kennedy, or the nine year period when he insisted Obama was a secret Kenyan Muslim, or that Clinton was so sick she was weeks away from death, or that he actually won the popular vote if you discount illegal immigrants, or the Muslims danced on rooftops on 9-11, or that Obama wire tapped Trump tower. It's just wanton just lies, free of consequence. He requires no evidence, and he only says these things because they play to the fears of his most rabid supporters. I suspect that the "informant" conspiracy theory is the same game all over again, completely fabricated but it pushes all the right buttons for Billy Bob in the MAGA hat who still believes the evil Obummer took away all our freedoms.