The bizarre thing is that the EOS M5 has focus peaking even though that mount has not had a single manual focus native lens released for it, whereas the EF mount has several. I would prefer to forgo the cumbersome adapter and mount my tilt-shift lenses on my 5DsR. But I wish Canon didn't force me to do that. My solution? Use a Metabones adapter and shoot with Canon tilt-shift lenses mounted on a Sony a7II, and use its native focus peaking ability. While you can install it using Magic Lantern, this may invalidate any warrantee. The best solution is to get some sort of guidance from focus peaking. Nor would you want to use autofocus confirm, which just isn't accurate on this type of lens. It is hardly a situation where you would want to be forced to set up on a tripod and use live view to focus. There are lots of articles on the subject:

I belong amongst a growing number of people who use tilt-shift lenses for creative portraiture etc. The trouble is that this is hardly the only use for a tilt-shift lens. You are meant to set them up on a tripod and use live view, zooming in to check your focus as you shoot architecture. In fact there are several manual focus lenses on offer in their current catalogue, namely their tilt-shift lenses: It seems that as far as EF mount lenses go, Canon's attitude is that they make no manual focus lenses.

It seems that Canon's attitude is that they make autofocus lenses and for that reason they don't need focus peaking on their DSLR bodies.

Magic lantern canon 5dsr