I've tried switching default browsers on mobile and copying the link from the app and signing in directly on a browser, but neither works. When I log in from the browser, it tries to open a link in the destiny 2 companion app, but the app can't process the request and just gives me the "open this link" or "decline" option on repeat. As stated, I can log into bungie.net through Steam easily on my desktop. Any help is appreciated.