Looking on Crutchfield and they don't list any head units available for the Prime, but do have a ton available for Prius Gen 4. I have to imagine the wiring / head unit in the Prime Plus is identical to the Gen 4, but before I take a swing and try to swap in a new stereo I was hoping someone who had done this before might clue me in.
Figure 86-03, Navigation & Front Monitor Display, in the parts catalogs for the 2017 Prius and 2017 Prius Prime shows that the same navigation receiver assembly made by Panasonic, with Toyota part number 86804-47330, is used on both models. (The small illustrations in the parts listings incorrectly show the larger unit.) You can confirm this is the head unit installed in your car by checking the ID number marked on the lower right corner of the faceplate; it should be 510053.
Has nobody been brave enough to do this yet? I have the same observation as @mkarolian after two days of ownership. Seems like any double din unit with the proper face plate (and possibly an iDatalink interface) should be able to do the job. With the idatalink option, many of the vehicle specific settings may be able to stay within access. I can't believe I've read 28 pages of thread titles in the audio section with zero efforts at rip and replace on the head unit. Maybe Priuses really are for old fogies...
IMHO; it's just safer and easier to install an apple to android translator box. That way you don't loose functionality and run the risk of unknowingly disabling something or set off error code Just my old fogies opinion
Trouble is there are many options, and sorting through them to get a reasonable choice has proven even harder than just researching head units. I think I may give this a go. I've got a Sony head unit laying here that shows on Crutchfield as being compatible with the regular Gen4, and with some wiring harnesses and such it should be a doable project for a half day. Probably can't do it until the week between Christmas and New Year's. I'll stop short of cutting wires behind the dash. Entune is so miserable that I'm willing to risk it.