Submodules are not the preferred way to incorporate third-party code for any environment I know. And while web-exposed URLs for management tools like Jira or AzureDevOps will need to adapt before the new default can be used, doing so even with a wholesale re-hashing of every commit isn’t technically difficult.

Well, like it or not, they are used. And not so rarely. Now, rehashing will probably work, but it will require every project to do that. If you use more than one submodule which is not under your control, you have again mixed hashes that you can't fix easily.