Day Packs (only one I've tested with so far) can be placed on Armour Stands, but they do not render on them.
Honestly, they probably shouldn't be able to be put on Armour Stands in the first place, since that may have bad interactions with mods that let you shift+rclick them to swap your armour with theirs since backpacks are supposed to drop items when unequipped (though I haven't tested if that is the case just yet)
1.3.5 for 1.16.5, Fabric Loader 0.11.2
Day Packs (only one I've tested with so far) can be placed on Armour Stands, but they do not render on them.
Honestly, they probably shouldn't be able to be put on Armour Stands in the first place, since that may have bad interactions with mods that let you shift+rclick them to swap your armour with theirs since backpacks are supposed to drop items when unequipped (though I haven't tested if that is the case just yet)