Compile Harfbuzz with Graphite support enabled.
InDesign 2020 uses Harfbuzz for complex script rendering. Harfbuzz has the capability to use Graphite instructions for rendering complex scripts, but Adobe has compiled Harfbuzz without Graphite support.
Graphite is needed for rendering some character combinations used in languages which are not supported by other font technologies.
Craig Webb commented
This would aid in correctly rendering Myanmar scripts, too!