The common practice today regarding tefillin is for them to be worn every ḥol day (give or take ḥol hamo'ed). Meiri on Brachot 14b describes various other practices, including one to which he seemingly gives his approbation:
וקצת חכמים נוהגים להניחם בימים שבין ר"ה ליום הכפורים אחר התשובה והטבילה והוודויין והדבר נכון בעיני
And some sages have the practice to wear them [tefillin] on the days between Rosh Hashana and Yom Kippur, after repentence and ritual immersion and confessions, and I agree with this.
Is Meiri saying that it's appropriate to only wear tefillin on the days between Rosh Hashana and Yom Kippur? Do we know whether this was the practice of his community (Perpignan), or neighbouring communities (greater Provence/Languedoc)? Do we know to whom he was referring with "some sages"? The edition of Beit HaBeḥira I have (ed. שמואל דיקמן) has no footnotes for this sentence.