[GNC] Report charts are empty on fresh 4.8 install

[Jason Spencer]

I have just upgraded to Linux Mint 21.1, and installed GnuCash 4.8
(1:4.8-1build2) from the distro sources. I opened up a file I had in my
prior install (2.6), and the file opened fine--all accounts and
transactions seem to be there. But when I run a report with a chart (say,
networth linechart or bar graph), the report is a blank screen. If I
inspect the chart source, the body is a table with 4 empty cells.

If I run a text-based report (e.g. Balance Sheet), I see the report text
and links fine, though it is scaled down to 6 or 8 pt font (though the
style section says 10 and 15 pt fonts.)

Is there some diagnostic I can run to troubleshoot the source of the
problem?