Which grains of bread need to be Pas Yisrael? Must gluten free bread be Pas Yisrael?
Only breads [or baked Mezonos products] that are made of the five grains [oat, spelt, wheat, barley, and rye] are forbidden due to Pas Akum. However, bread made of legumes or rice [or potatoes] is not included in the prohibition of Pas Akum. Nevertheless, legume bread falls under the prohibition of Bishul Akum and thus is only permitted to be eaten if the legume bread is not fit for a kings table. Some Poskim, however, argue that legume bread is never fit for a kings table, and is hence never forbidden neither due to Pas Akum or Bishul Akum. [Practically, all bread, irrelevant of the type of grain that it is made from, must contain a Hashgacha to verify that it contains only Kosher ingredients. Thus, there is no extra leniency associated with gluten free bread, and a Hashgacha is required. However, regarding whether it must be baked by a Jew, while non-Mehadrin Hashgacha’s would not be particular in this matter, a Mehadrin Hashgacha is to make sure that it is baked by a Jew even if it is made of grains that do not derive from the five grains listed above. Those who keep a Mehadrin Kashrus standard are certainly to be stringent in this matter.]
Is low quality grain bread which is not served on a kings table forbidden due to Pas Akum?
Some Poskim rule that low-quality breads made from the five grains which are not served on a kings table, are nevertheless forbidden due to Pas Akum. Other Poskim however rule that such breads are permitted, just as is the law regarding Bishul Akum.
 Michaber Y.D. 112:1; Rosh 19:21, brought in Tur 112:1; Rabbeinu Yerucham 17:7
 Michaber ibid
The reason: As these foods are considered of significance and bring towards closeness amongst people. [Taz 112:2]
 Michaber ibid
 Rama ibid
 Bach 112; Rabbeinu Yerucham Nesiv 17:7; Tur; Levush, brought in Shach 112:5 and Taz 112:3; Ben Ish Chaiy 2 Chukas 1
 The reason: Although actual cooked legumes is considered Bishul Akum, as it is served on a kings table, nevertheless its bread is not considered Bishul Akum being that the bread is not served on a kings table. [Ben Ish Chaiy ibid]
 There are various ingredients that bakeries enter into their bread which can be of Kashrus concern, and at times be explicitly not Kosher, such as: 1) Non-Kosher oils that derive from animals which are entered into the dough or placed to grease the pan 2) Hafrashas Challah if owned by a Jew; [See https://www.kashrut.com/articles/bread/; https://oukosher.org/blog/behind-the-scenes-theoretical-kashruth/the-local-bakery/]
 As a) Non-Mehadrin Hashgacha’s are not particular to require that bread baked by a gentile bakery [I.e. Pas Paltar] be Pas Yisrael, and b) Non-Mehadrin Hashgacha’s are generally lenient with their definition and inclusion of “Eino Rauiy Al Shulchan Melachim,” and hence in this case may rely on the dissenting opinion who argues on the Rama
 As a) The Rama rules that it is fit for a kings table and b) Perhaps today even the dissenting opinion would agree that it is fit for a kings table, as times have changed, and gluten free bread is served today by many fancy caterings.
 Peri Megadim 112 M”Z 3
 Avnei Nezer Y.D. 1:92-7 based on Shach