I think I have the same problem. Regardless of browser or smartphone OS, the logviewer cannot be started by clicking on the play button.
But I know that it used to work. Like you, I’m also having a look at Karaf via log:tail as an alternative.
I tried a clean/fresh install with no real THINGS etc, and the LogViewer works like that.
I have tried <Logger level="TRACE" name="org.openhab.core.io.websocket "/> to try and get some logging, but nothng shows up, even when using the debug Tool for Web Socket.