With regards to Chrome, technically they aren't stopping support for Java per-se. They have been rolling out a Netscape plugin API (NPAPI) depreciation plan since 2013. And currently Oracle Java still relies on the NPAPI. A quick Google turned up this suggesting that Oracle won't be doing anything any time soon to make Java work with one of the other plugin APIs (that Chrome supports). So in effect you are right; but it seems like a bit of a Mexican stand-off to me.

As for Spartan, that is slightly different (although somewhat the same) because MS never supported NPAPI anyway so Java has historically used ActiveX - which has been dropped in Spartan. So again technically it's not dropping Java support, just support for the plugin architecture that the Oracle Java plugin currently uses...

So at this point in time it looks like if you want to use any Java applets you'll need to keep Firefox and/or IE11 handy...

But back to your actual question (sorry for the side-track). I have no idea what the Webmin devs plan to do. FWIW TurnKey only package their software and pre-install it on TurnKey. We don't have any sway or influence. I would imagine that they will move towards a HTML5/Javascript implementation. But I only say that because it's what I'd do if I was a Webmin dev! :) I do not have any more info than you!

Instead they may say that Webmin File Manager only works in Firefox and IE11 and that if you want to use it, you need to use one of those browsers!?

So long and the short is that please ask Webmin devs. It looks like they have a mailing list and a forum. If you get a good answer I'd love to hear so please post back.

PS please excuse my rambling answer... :)

Just wanted to let you all know that an HTML5/JavaScript file manager appears to be in the works... A Webmin community member has implemented it and AFAIK the Webmin devs are doing QA on it with the intention of (hopefully) using it as a replacement for the current Java applet....

Please see this thread on our issue tracker for further info.