I can find only one accident (PAA 707, 1963) in which a jet transport aircraft was brought down by lightning. Better tank vent design seems to have overcome this problem since that time.
IIAF B747 Spain comes to mind and I'm sure that
IGH will have a page full of details on others
however you comment about better tank design and add in grounding of joints, flash arrestors etc. has made this cause even scarcer since these very old reports.