Could there be Temples Outside Jerusalem? (It appears there were)
Jewish Temple at Arad, Israel
Sanctuary at Arad
Excavations on the upper Arad, pictured here stratum X gate of Arad Fortress
Clay model house, 3,000-2,650 BCE
The temple at Arad was uncovered by archaeologist Yohanan Aharoni in 1962 who spent the rest of his life considering its mysteries, dying there in the mid-1970s.
In the holy of holies of this temple two incense altars and a "standing stone" were found, probably having been dedicated to Yahweh. An inscription was found on the site by Aharoni mentioning a "House of Yahweh", which William G. Dever suggests may have referred to the temple at Arad or the temple at Jerusalem.
The lower settlement and the upper Israelite citadel are now part of the Tel Arad National Park which have begun projects to restore the walls of the upper and lower sites.
Jewish Temple at Elephantine, Egypt
There was a whole colony of them, they built their houses and it seems set them around a small temple, at least according to the papyri.
Jewish Temple at Leontopolis, Egypt
he account of Josephus in The Jewish War, refers to the Onias who built the Temple at Leontopolis as "the son of Simon", implying that it was Onias III, and not his son, who fled to Egypt and built the Temple. This account, however, is contradicted by the story that Onias III was murdered at Antioch in 171 BCE. Josephus' account in the Antiquities is therefore more probable, namely, that the builder of the temple was a son of the murdered Onias III, and that, a mere youth at the time of his father's death, he had fled to the court of Alexandria in consequence of the Syrian persecutions, perhaps because he thought that salvation would come to his people from Egypt. Ptolemy VI was King of Egypt at that time. He probably had not yet given up his claims to Coele-Syria and Judea, and gladly gave refuge to such a prominent personage of the neighboring country. Onias now requested the king and his sister-wife, Cleopatra, to allow him to build a sanctuary in Egypt similar to the one at Jerusalem, where he would employ Levites and priests of his own clan; and he referred to the prediction of the prophet Isaiah that a Jewish temple would be erected in Egypt.
According to Josephus, the temple of Leontopolis existed for 343 years, though the general opinion is that this number must be changed to 243. He relates that the Roman emperor Vespasian feared that through this temple Egypt might become a new center for Jewish rebellion and therefore ordered the governor of Egypt, Lupus, to demolish it. Lupus died in the process of carrying out the order; and the task of stripping the temple of its treasures, barring access to it, and removing all traces of divine worship at the site was completed by his successor, Paulinus, which dates the event to c. March - August 73.
In his dig at Tell al-Yahudi in 1905/6, Flinders Petrie identified the remains of this temple.
Seems odd but plausible to me that some groups decided to build outside of Yerusalem knowing scripture has these 2 admonishments:
Exo 29:28 “And it shall be from the children of Yisra’ěl for Aharon and his sons by a law forever, for it is a contribution. And it is a contribution from the children of Yisra’ěl from the slaughters of their peace offerings – their contribution to יהוה. Exo 29:29 “And the set-apart garments of Aharon are for his sons after him, to be anointed in them and to be ordained in them. (ISR)
Descendants of Aaron were likely numerous so the above may have been adhered to.
Deu 16:5 “You are not allowed to slaughter the Pěsaḥ within any of your gates which יהוה your Elohim gives you,
Deu 16:6 but at the place where יהוה your Elohim chooses to make His Name dwell, there you slaughter the Pěsaḥ in the evening, at the going down of the sun, at the appointed time you came out of Mitsrayim.
Deu 16:7 “And you shall roast and eat it in the place which יהוה your Elohim chooses, and in the morning you shall turn and go to your tents.
The above would have difficult to participate in unless the inhabitants had heard directly from YHWH.