When choosing data to comprise chart; select a LONG colmn [of series].
Place cell cursor on first top cell of the series, then Shift+Ctrl+Down for one column until end of data and then Shift+Right for additional columns or Shift+Ctrl+Right until last data column, or starting from top left Shift+Ctrl+End for an entire data block below and right.
If the data is surrounded by empty cells: Ctrl+*.
Tested with LibreOffice 6.4.7.2 (x86); OS: Windows 6.1.
Which is slightly misleading, also in Customize Keyboard, because it is the asterisk on the numeric keypad, which on laptops usually is only available with some awkward Fn combination, if at all. The function is Select Data Area, if one wants to map it to some other key combo, for example Ctrl+8 (as Shift+8 is * on an English keyboard).