I tried to specify
:tend in my clocktable block according to the official documentation, e.g.
#+BEGIN: clocktable :scope agenda :maxlevel 6 :stepskip0 t :fileskip0 t :compact t :link t :tstart "<2020-12-27 Sun 06:00>" :tend "<2020-12-28 Mon 06:00>"
I also tried a minimum example of
#+BEGIN: clocktable :tstart "<2020-12-26 Sun 06:00>" :tend "<2020-12-27 Mon 06:00>"
However, only the clock entries from today seem to be produced. The
:tend are always ignored, for whatever reason.