They are not easy by any means. We found the only way was to the the lever to push the bead under the ARD towards the centre of the rim on both sides. This yields some slack so with strong thumbs and leavers with a good set of gloves, you can get them on.
Yep mostly this. Based on fitting a set of Rimpacts to my 650b+ rims. It’s easiest to seat one bead of the tyre first, then insert the insert. Then for the second bead, start opposite the valve and use a tyre lever to push the bead under the insert and into the central well of the rim all the way round then finish at the valve side with a tyre lever. Once you realise it’s the only way to do it, it’s actually quite straightforward.