Not sure but I think PrintPrism might work on some un-supported scanners too

[pharmacist]

I have to test this, but my first impression that by chance I tried to make a profile with PrintPrism with my unsupported Epson WF-7840 AIO scanner using the built-in ET-8550 scanning engine:

The scan histogram seems to be very healthy and this is the 3D plot in iccview.de with the same target scanned with the officially supported Et-8550 scanner (wired frame):

And this the softproofing with both profiles in PS (left with the test profile (WF-7840) and right with the profile made on the officially supported ET-8550):

 

[pharmacist]

Redoing the test with an earlier printed target on another paper type:

First on the ET-8550 scanner:

Secondly on the WF-7840 scanner:

Here is the iccview.de 3D plot:

Using both profiles in softproofing mode beneath: left original picture, upper right: softproofed with the ET-8550 profile (supported scanner using the dedicated ET-8550 scanning engine) and lower right: softproofed with the WF-7840 profile (unsupported scanner using the PrintPrism ET-8550 scanning engine):

below you can download both testprofiles in zip file to look at (note: this profile is not usable if you don't have combination: Netbit Glossy with the Inktec Powerchrome K3 ink (with original Epson PK en Violet ink) and the Epson SC-P900) and is only for demonstration/experiment.

 

[Ink stained Fingers]

As much as Epson is using the same printhead across a wide range of printers they'll use as well the
same scanning hardware across a similar range of printers. It would be just a matter of some tests - printing the patch file on several different printers by different users and comparing the outcome - how close the gamut volumes would match.

 

[pharmacist]

I have printed the target on a cheap cast paper of Action with the ET-8550, which should give a different 3D plot. I will redo the test this evening and see if the profile is similar using both the ET-8550 (supported) and the WF-7840 (non-supported) scanners.