Q: When a jubilee is celebrated in the Octave of Easter or Christmas, on a solemnity or on a Sunday, can the readings be changed???
A: A jubilee Mass would be a thanksgiving Mass that falls under the Masses for Various Needs and Occasions, and the rules governing them are in GIRM 374. A bishop may authorize their celebration on a Sunday in Ordinary Time, but not on “Solemnities, the Sundays of Advent, Lent, and Easter, days within the Octave of Easter, the Commemoration of All the Faithful Departed (All Souls’ Day), Ash Wednesday and the days of Holy Week.”
The jubilee may be celebrated on any day, but if it’s one one of those days in GIRM 374, then the presidential prayers and readings are those of the day, rather than of the Mass of Thanksgiving.