What is the geometrical structure of Pb3O4?
Maybe below 3d structure of Pb3O4 will help?

3d structure of Pb3O4

Also in the below link of a pdf, just before the discussion section the paragraph clearly states that there are both ionic and covalent bonds present in Pb3O4.

REsearch Paper on Pb3O4 structure

Thus we can conclude that it is Tetragonal, tP28 .(as per the link provided by Maxw in the comment to your question)

Also metals can form covalent bonds. Refer to below question and its answers:
Metals forming covalent bonds