Open external links in browser
Open links to sites outside of SharePoint.com domain in a browser by default. The SharePoint app doesn't handle 3rd party web app authentication well. For example, if you open your SharePoint Online site in the app and then select a link from a page in your SharePoint online site to your on-prem site, it gives a 404 error. The SharePoint app features also differ from what users expect to be able to do in their default browser with web apps other than SharePoint. After you select an external link in the SharePoint app, there is an option to open it in a browser, but users get the error message first. So they may not realize they can open it in a browser and have it work correctly. Another option would be to have a setting for each hyperlink throughout O365 to force opening in a new window or to open in the same window. Even if you left the default behavior as it is currently, it would at least give content editors the option to force one or the other to resolve the issues which result in external links being opened in the SharePoint mobile app. Without this change, we're stuck with promoting the web-only version of our SharePoint Online site to our employees instead of using the SharePoint mobile app.
Thanks for your consideration
Senthilkumar Palanidurai commented
I am also proposing the fix.