In case anyone is interested, there's two larger patches/patchsets for the Linux kernel GTP module currently submitted and under discussion on the netdev mailing list.
I'm not sure why this list was not copied, despite it being listed in the MAINTAINERS file.
See https://lore.kernel.org/netdev/20201211122612.869225-1-jonas@norrbonn.se/T/#... and https://lore.kernel.org/netdev/20201212044017.55865-1-pbshelar@fb.com/T/#u
Any feedback / comments / review or even testing is appreciated.