This was with Zwift with a pretty beefy gaming rig (1080 Ti), and I can run games like Farcry 5, Ghost Recon, Warframe and the like at top end settings with no problem at 1920x1080.
I don’t ever see any frame rate type problems (I am not monitoring it quantitatively, however).
I have a background in coding and game design from the late 80s onwards, but I have only done modern “AAA” work in UR4 and not used any other engines.
So, I do not have enough expertise to come up with an explanation why the scene lighting would flicker as it did. When I overload my own work with too many actors/lighting etc. what I see is an overall frame rate drop and/or processing delay in getting all the actors moving (I do push it sometimes). I have never seen such a thing as when the scene flickers. That is only in UR4, however.
The Junge is HANDS DOWN the most glorious Zwift region with the 3D aspect of the trees as one rides through them - not to mention the overall atmosphere and ambiance.
One thing I learned long ago as a game designer is that you want to design for the state of the art hardware because by the time you have all the bugs worked out and your project published that “state of the art” will already be getting obsolete.
Way back in the end of the 80s and early 90s I spent a huge effort to make my game software (K-12 learning games) run on the old Macs (I had customers in convents who only had old tech). It was quite a bit of work, and of course when it was all finished most of those customers had already upgraded their hardware to the new fangled color displays! Oops.