Nothing there, no. I'm a Kubuntu user and the only Linux option listed was abandonware for Arch. The only thing that I could find was the "Open in <X> browser" series of browser add-ons by Andy Portmen. I did a little testing, and it did at least seem to work, for the brief amount I used. I am just a little uneasy relying on it. While my Google-fu may have failed, it was the only solution I could find for my use case. My main browser is Firefox and my KoL browser is Chromium, and the particular extension I need has less than 150 users, so if the developer gets bored of keeping up with it I may get stranded hoping to find another solution that may not exist.
Granted, I'm not married to either browser. But I am kind of wedded to having KoL separate from my general web browsing.
I may be in the extreme minority and this will be a feature that never returns, and that will be okay, but felt it remiss of me to not speak up and let you know that there's a least one user that wants this feature.