At one point, there were three people claiming to be the Bishop of Rome.
One in Avignon claimed to be Benedict XIII. One made Pope Rome was Gregory XII. One proclaimed Pope at Pisa was John XXIII.
All of them had supporters and detractors. In 1415, Sigismund of Luxemburg tried to end the mess by reconciliation. He had Gregory and John both agree to hold a council. John wanted Rome, but it was done in Constance. John fled and was accursed of Sodomy, Piracy, and Heresy. He was sheltered by Frederick von Hapsburg, Duke of Austria, which later cost the duke his county in Switzerland.
Let's suppose John XXIII was recognized by England, France, Portugal, Bohemia, Denmark, Castile, most of Northern Italy, Venice and parts of the Holy Roman Empire. Benedict XIII recognized by Aragon, Sicily and Scotland. Gregory XII is favored by Poland, the Palatinate, the princes of Bavaria (but not the Bishops), and Naples. That list is actually close to OTL.
Then John attends and agrees to step down without a fuss. OK... does anything interesting happen in the next 3 decades?