Added Kensington SD5700T to unsupported, although in the future it may work.
I tried with Ubuntu 21.04, worked very, very briefly. Maybe 20 seconds. Enough to give me hope, then nothing. Rebooted, unplugged and plugged back in, power cycled dock, etc., just wouldn’t come back. Went into Windows, same thing, eventually one of the power cycles got it to work in Windows for ~20 seconds again. Spoke to Kensington support, they asked me to try another laptop… plugged in my Dell XPS 15, worked flawlessly. The support agent suggested since the Framework isn’t TB4 certified yet they can’t really do much to assist with getting it working. Meaning, hopefully, in the future it will work. I say hopefully because… it’s a pretty dang nice dock, works with my XPS 15 better than my WD19TB does.
They did suggest the Kensington SD5600T, because it’s TB3 & USB 3.1 backwards compatible. So, although it might not “work as well as it could” it should still work. Might give it a shot, but having trouble finding one that ships fast. I’ve got the week off work, would prefer finding something that I can know works so I can spend some time rewiring my desk, but don’t want to commit to doing that until I have the new dock sorted…