Thanks for above information. Based on that I tried to fix this package. I created https://github.com/pnemade/fontforge/commit/94a19c782cec508cbfb9ed9ff2e1cbbfd433ba10 and used for local fontforge build. But it is failing with many undefined references.
/usr/bin/ld: .libs/libfontforge_la-python.o: in function `_Py_INCREF':
/usr/include/python3.8/object.h:459: undefined reference to `_Py_NoneStruct'
/usr/bin/ld: /usr/include/python3.8/object.h:459: undefined reference to `_Py_NoneStruct'
/usr/bin/ld: /usr/include/python3.8/object.h:459: undefined reference to `_Py_NoneStruct'
/usr/bin/ld: .libs/libfontforge_la-python.o: in function `PyFF_hasUserInterface':
/var/home/parag/rpmbuild/BUILD/fontforge-20190413/fontforge/python.c:1524: undefined reference to `_Py_FalseStruct'
/usr/bin/ld: /var/home/parag/rpmbuild/BUILD/fontforge-20190413/fontforge/python.c:1524: undefined reference to `_Py_TrueStruct'

Will check more on this on Monday.

The undefined references are caused by a change that is described here: https://docs.python.org/dev/whatsnew/3.8.html#debug-build-uses-the-same-abi-as-release-build ("To embed Python into an application...").

tl;dr use python3-config --embed (or pkg-config python3-embed)

Thanks for the help. I am going to use another (Fedora specific) patch to fix above issue , I am not able to make it fallback using m4 language

diff -urN fontforge-20190413.old/m4/fontforge_arg_enable.m4 fontforge-20190413/m4/fontforge_arg_enable.m4
--- fontforge-20190413.old/m4/fontforge_arg_enable.m4   2019-04-13 13:08:39.000000000 +0530
+++ fontforge-20190413/m4/fontforge_arg_enable.m4       2019-07-21 16:31:27.939734401 +0530
@@ -116,8 +116,8 @@
 if test x"${i_do_have_python_scripting}" != xyes; then
    i_want_python_ver=
 else
-   PKG_CHECK_MODULES([PYTHON],[python-"${PYTHON_VERSION}"], dnl   [PKG_CHECK_MODULES([PYTHONDEV],[python-"${PYTHON_VERSION}"],,[i_do_have_python_scripting=maybe])],
-      [PKG_CHECK_MODULES([PYTHONDEV],[python-"${PYTHON_VERSION}"],,[i_do_have_python_scripting=no])],
+   PKG_CHECK_MODULES([PYTHON],[python-"${PYTHON_VERSION}"-embed], dnl   [PKG_CHECK_MODULES([PYTHONDEV],[python-"${PYTHON_VERSION}"-embed],,[i_do_have_python_scripting=maybe])],
+      [PKG_CHECK_MODULES([PYTHONDEV],[python-"${PYTHON_VERSION}"-embed],,[i_do_have_python_scripting=no])],
       [i_do_have_python_scripting=no])
 dnl dnl TODO: have python3 AND python2, but only have python2 dev, but no python3 dev
 dnl if test x"${i_do_have_python_scripting}" = xmaybe; then

So proposed changes failed the scratch build in f31 -> https://koji.fedoraproject.org/koji/taskinfo?taskID=36440030
Yes I know python-3.8 is not in f31 but then I need to find some time to make fallback work in above patch. Simple if...else...fi not working.

Apply patch conditionally? Not the best solution but should work:

%if 0%{?python3_version_nodots} >= 38
%patchX
%endif

Thanks. I have used above conditionals and fixed in new fontforge build fontforge-20190413-2.fc31

BTW, I tried many ways to fix https://github.com/fontforge/fontforge/blob/master/m4/fontforge_arg_enable.m4#L119 but there is really no python version information available or PYTHON_VERSION value available in that m4 file to add fallback cases.

The patch is not part of the SRPM, preventing us from running easy rebuilds :(

Would you mind always keeping the patch in and apply it conditionally?

Similar thing as in: https://docs.fedoraproject.org/en-US/packaging-guidelines/#_no_arch_specific_sources_or_patches

Hopefully fixed in fontforge-20190413-4.fc31 build.

Thank You.