You are correct... seems there is a "time-lapse" camera app available as an extra purchase from Sony.
At a quick look it appears that the a6500 is the most recent model with support. Last updated in 2016. Sony lists it under the "Playmemories" heading, which has apparently been superceded by Imaging Edge.
Sorry for the incorrect info. Glad you found a solution. Note that it is possible that shooting stills in interval mode and creating the movie on your computer (as opposed to in-camera) _may_ provide more flexibility and/or better quality.
When I do time-lapse, I shoot RAW and then process the files in Lightroom. This gives me full control over post-processing. That may or may not be important to you.
A follow-up to my own question, in the event someone else has the same issue.
Touch track DOES work in 4k mode.
Not sure why I couldn't get it to go. A Sony rep helped me out - ended up resetting the camera to default settings, enabled the necessary menu items and it now works. It may have been a related setting or just s glitch. Either way, it is working now.