I see some here are asking for Safari on Windows and Linux. You can get most of the way by just running Webkit builds on those platforms. BUT! That would only solve a small fraction of issues. Most of the issues my team has to work around are only with Safari on iOS and ipadOS. Plenty of those issues are so OS/hardware specific that they need to be debugged with actual devices since they can't even be reproduced in Xcode simulator. Those issues are mostly related to audio, webrtc and touch.