The transition of EVE downloadable data from XML tables to SWAGGER has reached the point where the old system has been discontinued, which leaves me no choice but to convert.
SWAGGER is more complicated as it uses temporary tokens to get access to private data. This allows third-party apps to display your secret stuff without having access to your password, and that isn't easy to implement with a spreadsheet! However, a nice person wrote a guide:
Right now I have the tables up and running, the next task is to get the many spreadsheet references to point to them. Which, with INDEX MATCH arrays, is a pain.
[added] Finished! Took six weeks!! Everything seems to be back to normal, updating generates a lot of error messages but these can be ignored.