I export everything in rec709. To be honest, all this hdr stuff is giving me headaches. Not just for Star Wars but at work too - there, at least, we have a dedicated support team for this stuff. 😀
For what it’s worth, it’s possible use Rec. 2020 without any HDR. There is a benefit to it, albeit small. Some commercial discs do it, and (UHD) player compatibility is not an issue.
The downside is that you’ll be inviting questions like “Why didn’t you do HDR?”. But to be honest, those questions are going to happen regardless!