Created attachment 216643 [details] freecad-py38.patch FreeCAD doesn't release frequently, so let's import the upstream patch. It's a one line fix.
A commit references this bug: Author: cmt Date: Wed Jul 22 20:31:05 UTC 2020 New revision: 542892 URL: https://svnweb.freebsd.org/changeset/ports/542892 Log: cad/freecad: fix for python 3.8 PR: 248153 Submitted by: Greg V Obtained from: https://github.com/FreeCAD/FreeCAD/commit/6eacb17b3e03d20 Changes: head/cad/freecad/Makefile head/cad/freecad/distinfo
committed, thanks