To enable certain Apple app features (Sign in with Apple in this case) Apple requires that you register an associated web domain. This domain needs to host a file called apple-app-site-association (with no extension) in the root of that domain.
I am looking for a free way to do this. My developer website is hosted by Wix website builder. Wix will not allow you to upload files with no extension. Even if they did, I'm not convinced that their domain system would allow it. Wix domains follow the pattern of https://{YourUser}.wixsite.com/{YourWebsite}. Apple would look for the file at https://{YourUser}.wixsite.com/, a location which you have no control over. I believe that the other free website builder, Squarespace, suffers in the same way. Someone found a Cloudflare workaround, but Cloudflare no longer works with either website.
I didn't know it would be such a pain to put this file somewhere. What is the best solution to this? I'm surely not the first person to stumble into it.
I wasn't able to get a working solution with any of the standard website building platforms. I was able to get two slightly different solutions working though. GitHub Pages is free and lets you set up a repository that meets the requirements for Apple's file. Firebase lets you do the same thing through their "Hosting" service, in the free tier. On Windows you will need to use command prompt to create a folder that begins with a period for both repositories. GitHub Pages can be uploaded to from any Git program, Firebase Hosting requires you use their command line tools package.