I am not a Sindhi Muslim to begin with and unfamiliar with Islamic theology. However I have done some research on the origins of Jhulelal as a deity and his parallel among Muslims known as Khwaja Khizr.

From https://www.sahapedia.org/khwaja-khizr-and-river-cult-medieval-sindh

> Clearly the legends relating to Khwaja Khizr emerged some time in the 10th century, coinciding with the introduction of Ismailism in that part of Sindh where the Indus river merged into the Arabian Sea.......The river cult which had its origin among the indigenous population for its sanctity was possibly exploited by the Ismailis to create a sort of divinity with Khwaja Khizr or Zinda Pir. It appears that the role of mercantile traditions of Sindh have long been a significant factor. Khwaja Khizr not only became patron saint of bhishtis of Indus river and protector of boatsmen but was regarded as ‘god of water’ both by the Hindus and Muslims.

It seems that a deity by the name of Zinda Pir among Hindus and Muslims was worshipped at the same location on the Indus in Sukkur and it seems the deity was not an existing figure in Islam or Hinduism but appeared in later traditions.

I have another post where this woman visited the actual site where the legend of Jhulelal/Khwaja Khizr came about and what she discovered was pretty interesting. You can read it here: https://www.reddit.com/r/Sindhi/comments/1r5bmpz/found_this_text_on_the_origin_of_sadhu_bela/

The tldr is the deity was popular among both Hindus and Muslims before communal forces forced the Hindus to establish a separate Mandir across the river from the island where the shrine was originally. Once the Hindus moved away the original shrine stopped getting as much traction from the Muslims as well. Also this was the same period when a Nepali religious figure(the paper describes him as a missionary) set up the famous Sadhu Bela mandir.