What appears to be missing for external mice (e.g. MagicMouse) is macOS-standard "velocity scrolling" (AKA accelerated, 'elastic', over-scroll etc.)
i.e. in Safari scrolling on trackpad and MagicMouse feels exactly the same, hopefully the same can be true in Orion.
EDIT: actually natural macOS scrolling via MagicMouse works fine on orionfeedback.org (and theverge.com), but not linkedin.com for instance… so seems more limited in scope (using 0.99.109.1.4-beta)
EDIT 2: could've sworn I saw it working OK on twitter.com, but tried again and velocity scrolling is not present on Twitter… is it possible this behaviour could toggle based on site JS/scroll jacking, i.e. something normally blocked that's leaking through under certain conditions?
…or I'm just making up voodoo!?