UI Implementation with different OS tested with different Browser

We tried to design a OS and Browser independent website. Our working devices had three different OS systems: windows, linux, macOS (which is based on linux but still works different). We first ran into the issue that our application was Linux and MacOS compatible but not for windows. After solving that by adding some settings our windows developer started to implement our first UI which worked pretty fine for him in Chrome and Mozilla Firefox. Then we started testing on our Linux device in Chrome and Opera where the page looked exactly the same but some of our buttons didn't react to our clicks in Opera. After that we decided to test on our MacOS device in the Safari Browser where we ran into the next issue: the buttons didn't work as well but additionally to that we couldn't scroll in the view anymore after zooming into the content. In Chrome it worked on each device. Reason for that was, that a specific Version of Kendo blocks some Safari Actions. For the Linux Device we didn't manage to fix it specifically but since it worked with the new kendo version we also guessed that this was a version issue.