Was not Pope John XXIII another under suspicion of heresy as Fr Roncalli?
I've not seen that in print.
However, the day of his funeral, the local president of the Italian Communist Party closed his office in mourning. Numerous accolades were poured out on Pope John ( who, from all reports, was an exceedingly gracious man ) by many enemies of the Catholic Church. This phenomenon was widely reported.
However, I don't know of any reports of any of those nogoodniks converting to the Catholic Faith.
FWIW, I think Pope John was a jolly old soul who truly did wish to have remained a little pastor in a little Italian hillside parish, visiting parishoners, sampling some nice fresh-made pasta and a glass of vino, and saying his prayers. He said that Himself, I understand.
He did, after all, write an encyclical formally
promoting and protecting the use of Latin in the sacramental Rites. Which, of course, was trashed by the hellions running the Council at the earliest possible moment.
On the other hand, I have read that Paulo Sesto, a rising figure under Papa Pacelli, was discovered to have been privately "negotiating" with know Commie representatives and, when found out, was air-expressed by the pope to a town from which it was wished he would never be heard, again.
That didn't work out so well, though.