@Keychat is a better optiin for web apps on mobile than using PWAs. Signing into PWAs using Amber generally requires NIP-46 signing, instead of NIP-55, which is used for native apps like Amethyst. I have always found NIP-46 signing to be inconsistent at best. Keychat allows you to use NIP-55 with Amber to log into ANY web app, because keychat converts it to NIP-07, as though you are signing in using a browser extension. It's much more consistent. NIP-46 can work, but it is highly dependent on the relay you are using for it, and I think there must be a very short timeout window where, if the client doesn't see the signed event in time on the relay, it just doesn't log you in.