Just a couple of quick things here:
Three years ago, I had a teammate write a migration guide here: CEP-Resources/UXP-Migration-Guide at master · Adobe-CEP/CEP-Resources · GitHub
I think there’s been at least one update to UXP since it was written, but I’m not always right.
Built-in scripts that come with the latest Photoshop packages still use old school ECMAScript 3 code, so you haven’t even tried to migrate them even after so many years that UXP has been around, so we are a bit skeptical about migrating because you also haven’t migrated these old built-in scripts.
The built-in Photoshop scripts are written in ExtendScript, right? CEP is being slowly phased out over time, not ExtendScript…
That said, I remember a thread where someone was saying you have to launch Photoshop in Rosetta to run certain old scripts.