Yeah… personally I don’t use the APVST for non-automatable paramater-like data at all. That is, I immediately stopped doing it once I figured that there are hosts which ignore the non-automatable flag (I’m looking at you, Reaper!). It’s ridiculous how quirky all of this is. While JUCE does a good job in general abstracting the individual plugin format quirks away and applying some specific workarounds for extra quirky hosts, I hope that at some point the industry will adopt a new and better thought out standard. CLAP is an obvious candidate, even though I haven’t tried it myself.
From what I can tell with the latest version of JUCE (7.0.4 as of now), updateHostDisplay works well enough for reporting changed internal state, and some special host-specific functionality that would be nice to have, but is not the 99% default use case, stays more or less unfixable.
Couldn’t resist the little rant 