Hi ahoward, Kirk,
This morning I was able to reproduce positive results using the Bob workaround. Affinity did crash on me once, but I'm now convinced that, well, its Develop Personna just might not be as stable as it should be. Logical reflection suggests that the sidecar thing is not an issue. If Affinity is just being passed the path for the file, it can't have any idea at that point that the sidecars even exist. So that can't be a thing.
I read the Serif posts about the MSIX vs MSI/EXE issue, logged onto my Affinity account and confirmed that for at least my 2.5.x version, you can choose between installers when you download. But the MSIX appears to be the default. I now assume that my download was MSIX. So, it looks like many users will find themselves with the "Windowsapp" installation. It may or may not be trivial to uninstall the sandboxed version and install the normal version. I don't know what might happen to workspace customizations, preferences, and the like. I'll explore some more.
Serif's principal reason/excuse for using the MSIX installation seems to be that they can do updates as patches, thus saving "the user" the bother of downloading the whole installer for upgrades. Seems a tad disingenuous to me, given that server bandwidth might be a bigger deal to the vendor than ISP bandwidth caps might be for the user. But I'm just a cynical guy.
Bottom line seems to be that the need for Photo Mechanic to have its own solution won't go away, at least not soon.
Meanwhile, I think that my now-hopefully-moot issues with ACR may have stemmed from impatience as much as my just being a potato-head. Both ACR and Affinity Develop churn away silently at opening files. Multiple files mean longer churning and more user antsyness.
UPDATE: Figuring that if I was going to move Affinity Photo from Windowsapp-land to the normal program files directory, I should do so now before I have a ton of time invested in customizations and downloaded plugins and whatnot. So, I downloaded the .exe installers for all three programs, uninstalled the existing ones and reinstalled with the new installers. Reactivated with my password. And it was fine. My Affinity workspace was as I left it. (Meaning the uninstaller had left my prefs files in Appdata alone, which is both a good and bad thing.) I then set Photo Mechanic's launching preferences to the new location of the photo.exe file and all was well.
Cheers.
-Carl