In 2018 the Pontifical Commission Ecclesia Dei granted an ad experimentum indult to a number of traditional religious orders and societies to celebrate Holy Week according to the pre-1955 usage. (It should be stated that for the priest who is not a member of one of these orders or societies, a particular indult should be sought before celebrating the pre-1955 usage in a parish, though it seems that these have been given freely in the past.) Interestingly, the recent publication of the Vatican edition of the 2021 ordo for the Extraordinary Form also includes permission to offer abolished feasts and observe some rubrics which were removed from the general calendar in 1955, provided those practices are customary or devotional to the faithful in that place.
Source: Adoremus Bulletin for March 2021: Vol. XXVI, no. 5, article de l'abbé Aaron Williams en ligne.