Hi Richard,
In an attempt to try and answer your question about updating the AIRAC via the EFB, I removed the 77w update using the Hub, cleared the whole of the cache (i.e. all the contents of …WASM\MSFS2024\pmdg-aircraft-77f) and restarted the sim. The regenerated data (without AIRAC 2603, of course) had the desired effect of removing the WASM crash, but in the absence of navdata the IDENT page on the CDU shows no version (see pic).
However (albeit contrary to PMDG’s current recommendation), I was then able to go to the EFB and try to update from there — but as expected the loading process stalled about two thirds of the way through.
(It also unhelpfully reset all my preferences, and cleared my SimBrief Alias and Hoppie ID).
So the WASM crash was removed along with AIRAC 2603, but I am currently unable to plan routes in my 777.
Anyway — hopefully, that answers your question.
[Later edit] - in desperation, I tried substituting the 777-300ER msfs_navigation_data_interface.wasm with the downloaded version from https://forum.navigraph.com/uploads/short-url/25JJ8QRWSTx6EuidMB5xjXrZKEg.wasm and then trying the EFB update again, but complete failure — the progress bar didn’t even begin to move. Ah well, I tried.
And I can confirm that the path you gave (C:\Users\brian\AppData\Local\Packages\Microsoft.Limitless_8wekyb3d8bbwe\LocalState\WASM\MSFS2024\pmdg-aircraft-77w\work\NavigationData) does contain the navdata files for AIRAC 2603: it’s just that the aircraft is unaware of that, seemingly.