Thanks for help, Victoria and Jim!
I did manage to download and install lightroom 6.14 now, yeaay!
Though I again ran into the problem that it wouldn't sign me in to adobe, claiming I don't have internet connection (which I have). I had same issue yesterday when using my old 6.0 installer, but then it gave me the option to do this offline using procedure described at adobe.com/go/getactivated
This time this option to generate offline response key was not available during installation of 6.14, and I hope my lightroom will not get disabled after 7 days.. if it does, I will probably have to wipe it and try again.
I would already sign up for CC, even though I don't use lightroom often enough to justify the subscription, but my old mac is not compatible with system requirements, and at the moment I am not ready to change it.