So how do we get to that chest?

You will find more of them that you can't get to. I think they are broken atm.

If it is the one I am thinking of, misty step worked for me.

Thank you, i went back to a save point prior, took Misty Step at the level 3 level up and that did it, appreciate it!

No probs.

Korzad i have been able to get all so far with Jump and Misty Step.

I will have to try misty step for it then. But Levitate, spider climb, and jump have not work for me. 

Can confirm Misty Step works. Seems odd that all the other choices do not. Also, I got fly and that didn't work over water. But misty step did.

The only one I didn’t get was at the final castle just north of the guy with the wolves   Fly and jump didn’t work. Didn’t try misty step yet. 

Yep, I tried spiderclimb and jump first before misty step (though that was before I had figured out that encumbrance impacted on jump distance). Not sure if the rogue version works (I think it is called dark step), as I went with a thief for my rogue.

The only one I didn’t get was at the final castle just north of the guy with the wolves   Fly and jump didn’t work. Didn’t try misty step yet. 

Misty Step worked for this one as well. But in my game, I could not access the tree stump. It showed with tab but couldn't interact with it.

I also tried flying to get to that chest - but it says no path. I don'thave misty step sadly.

There are two chests I can't get to in the tower. One is behind the outer wall with some scaffolding that could be toppled over if you're on the other side. Maybe it's possible to get there later ?
The other is on top of some pillar: https://pasteboard.co/Jyx6Ayk.png , that you could supposedly reach using a ladder, but if using the ladder it does not do anything.
Seems quite inconsistent to me to limit access like that.
Levitate seems to be prominently bugged, as I can't even cross chasms I can easily jump over anymore. So weird.

The one with the ladder you can get to (but not before your mage is level 4 I believe).  You levitate first and then use the other spell to jump on the platform.  As far as getting back down, I was able to do it with the fly spell.  And for the other, in chest, since the new update, I haven't been able to access yet.

You can no longer get to the first one. I am pretty sure that this was a result of the changes that prevented characters from being pushed off ledges.

The second one you can get to but you need the fly spell. AND you need to have cast fly on the opposite side of the pillar as the ladder (or at the least with no jumpable gaps between you and the place you want to fly to). The fly spell is currently bugged, likely because of the changes that prevented characters from being pushed off ledges and cannot move a character to any point where, if the spell ended, they would be unrecoverable. And so depending on where you fly from you will be unable to get to the chest with the non-working ladder.

And similarly never be able to get to the chest that had the scaffolding that could be toppled over if you could get to it.