When playing a standard definition video, or a 720p/24 video, is there any way to completely avoid upscaling?

Just to note that this has been working correctly on the Vero 4K for a long time, now. But you do need to use the whitelist feature to make it work.

Please check out my whitelist guide for the settings: [HowTo] Guide to the Kodi whitelist function and related settings

In particular, you need to whitelist 480p and 576p modes, and set “Display 4:3 videos as” to “Use HDMI AVI Signalling”. But see my guide for more detail.