I am now taking a lot of 4K video of wildlife. With Lightroom 4 I can easily capture a frame from a video and save it as a jpg.
I would like to update to a newer version and downloaded the trial version of Lightroom CC. I see no way to capture a frame.
I have found a tutorial that shows how to do this with Lightroom Class CC.
Will Lightroom CC ever offer this capability? Is it there now but I cannot find it using the trial version?
It doesn't do this currently. You want Lightroom Classic which is the real sequel to Lightroom 4 you are used to. Lightroom CC is a completely new app that misses 95% of the features of Classic but that stores its entire catalog of images in the cloud instead of on your computer so they are available anywhere. It's really for a different set of people and way of working and it is unfortunate that Adobe chose to name it the same as the existing and continuing product that we all knew as Lightroom. Over the coming years, Lightroom CC will undoubtedly gain some features that are currently missing. You can ask for new features here: https://feedback.photoshop.com so they can be prioritized but it makes most sense currently to just use Classic for this as it might be a few years.