Thank you very much, Doug, this is really helpful! Yes, definitely need to continue digging deeper.
I understand your approach and the link is very helpful! I assume I need to be very careful that any checker image has the right profile embedded and that PhotoShop uses that. When printing absolute colorimetric from PS, I am getting a warning that I should rather use the Adobe Color Printer Utility, if I want to to print a calibration target without color management. I find this a bit confusing, since there is clearly a difference between printing with absolute colorimetric vs. no color management and I am wondering, if the former still works perfectly, or if PS has partially switched off support for this.
I am generally surprised that there isn't a more systematic way for this kind of verification process included in my x-rite i1Profiler application. Isn't it a very common use case to test the accuracy of a printer profile? So why can I not just choose a calibration patch set in the app, print that *with* the profile I want to test, scan the print, and get a bunch or error metrics, like average/max/min dE, etc. After all, the i1Profiler has all the info needed (correct Lab values, etc.) and 90% of that work flow is identical to creating a new target, so it's already there, except for the final comparison step. Maybe I am missing something. Also glad for any pointer to a different app that would provide this kind of workflow, which would avoid having to figure out the Lab values for my checker image and then do very manual comparisons.
Lastly, what should I expect good to look like? I vaguely remember seeing a post that said dE of 1 is about as good as it gets. But not sure, if I should expect to reach that with my printer/setup and if I even need that.
Thanks again!