Studying Torah when a relative passes away during the festival

If someone's father passes away during Chol HaMoed, can he study during the festival until he begins the seven days of mourning after the festival?

In the Gemara Ketubot, page 4a, it states: "Rabbi Yochanan said: Although it is said that there is no mourning during the festival, private matters are observed." The Rosh and Sha"r write that the version in the Gemara is "festival," and therefore one who buries his dead during the festival observes private matters, even though after the festival he begins counting the seven days of mourning. However, Rambam in Chapter 10 of the Laws of Mourning writes that during the festival, the laws of seven days of mourning are not observed at all, even in private matters. Ramban explains Rambam's opinion that he holds there is no mourning on Shabbat. And specifically, Shabbat, which counts towards the seven days, observes private matters, but festivals, which do not count towards the seven days, do not observe mourning laws, even in private matters. In Shulchan Aruch Orach Chaim, Siman 548, Seif 4, it states: "What we said that one who buries his dead during the festival does not have mourning apply to him, this refers to public matters; but private matters are observed." And similarly, in Yoreh De'ah, Siman 399, Seif 1. Mishna Berura, Siman 548, Seif Katan 16, writes: "This refers to bathing in hot water and marital relations, and Torah study in this case is forbidden, and there are those who permit Torah study, but regarding being called to the Torah during the festival to join the minyan of those called, it seems that initially it is not advisable." From his words, it seems he concluded that it is possible to be lenient with Torah study during the festival. And similarly, in Shu"t Chacham Tzvi, Siman 100: "If he does not study, he will sit idle, it is also permitted, for in the laws of mourning it is not proper to study during the festival, one can rely on Rambam and his supporters to study on Yom Tov all the commandments of the Lord are right." In Pitchei Teshuva, Siman 384, Seif Katan 1, he is puzzled by this and writes that it is forbidden in private matters, and writes that it can be reconciled according to what is written in Siman 393 in the name of the Shridei Esh, that it is forbidden during the festival only in private matters, it can be reconciled. Nevertheless, the custom is to forbid all private matters, as Mishna Berura writes, but in Torah study, it is customary to be lenient. And they rely on Rambam's opinion that there are no mourning laws in private matters during the festival, combined with the opinion of Chacham Tzvi, that it is forbidden to study in forbidden matters during the festival, and since we hold that one must study even during his days of mourning, he can study in permitted matters.