I can now confirm this works with debian stretch
I've used "RobertCNelson's image for console" , more precisely the one of "7th January" , running kernel 4.9.74-ti-r90
On top, I've installed the raspbianstretch build of tvheadend:
deb https://dl.bintray.com/mpmc/deb/ raspbianstretch stable-4.2
So far, it's been operating within the parameters :-)