Theoretically, there should be some views of the very top of 6X, Independent, and the Austonian from as far away as Luling (~40mi as the crow flies) or even Longhorn Cavern in the Hill Country (~45mi). I went to
https://www.heywhatsthat.com/ and used their horizon finder tool with an elevation above ground at approximately 600ft at roughly 6th and Congress to get the view map. Everything in red can be seen by (and thus see) someone here.
I know the tool doesn't take trees, buildings, or atmospheric effects into account to calculate these views, but on a clear day this summer maybe someone with a drone (hint hint) could go out to some of these places and try to get a record for the farthest Austin skyline pic on the forum.