file:////calc1.xlsx likely is not the correct URL to your file’s location, this example assumes that the file calc1.xlsx resides in the root directory, which likely it does not. If it is in your LibreOffice document folder then try to enter the formula with ‘calc1.xlsx’#$Sheet1.$A$1:$A$5 and the correct full path will be displayed afterwards. If the file resides somewhere else then use the full path URL, e.g. 'file:///home/you/path/calc1.xlsx'#$Sheet1.$A$1:$A$5
If you tried to directly enter the external reference into the chart data range dialog that does not work, you’ll have to fill cells in the local document first, for example by entering ='file:///home/you/path/calc1.xlsx'#$Sheet1.$A1
in one cell and then pulling down the formula 4 more rows, or entering ='file:///home/you/path/calc1.xlsx'#$Sheet1.$A$1:$A$5
as array formula (Shift+Ctrl+Enter).