Hello all,
We are about to move with our 2 huskies (9 and 6 years old) to a new apartment in Switzerland, which I am realising is heated by radiant floor. Since they always tend to like cool spots, I have become worried that it might be an issue for them. Does anyone have experience with this kind of heating for them? Might it be a serious problem that merits finding an alernative apartment?

Radiant floor heating and dogs - no help.  
Radiant floors - love 'em!  Several years in Korea where all the floors are heated.
Dogs - the radiant floors are warm so they'll probably not be too impressed.  I'd be thinking about a raised bed for them.  During the day, it'll probably not be a problem but you might find yourself with some restless dogs at night as they go looking for a cooler space to sleep.

We had warmed floors at our last house. Not true radiant but our furnace was under the floors and it worked in a similar way. They would stay on the tile by the door which tended to stay cooler than the wood that ran the rest of the house. This was probably due to weak door seals that would allow some cool air to hit the tiles. Outside of that one spot they stayed elevated the rest of the time up on the couch which I can't imagine was much cooler. For the most part we didn't keep things too warm. Our house is about 68f (20c) in winter which is tolerable for mine. The elevated bed as was mentioned will be your easiest bet if they will use one. They do make cooling mats but it would be a constant hassle bringing it in and out to chill it but could be an option if the dogs are keeping you up at night because of restlessness from the heat. You could offer a cooling mat at night to help calm them.

I've had two of those "cooling mats."  One required that it be chilled before use (a major PITA!) and the other depended on conductive cooling where it absorbed the dogs heat, transferred it to the 'filling' and, in theory, radiated it out to a cooler atmosphere - didn't work well at all when my "cooler atmosphere" was roughly 90f.

Of the two, one lasted a couple of days before Avalanche decided he wanted to move it around.  He grabbed it with his teeth, pulled and got a mouth full of something that didn't taste good.  Anger making part was that the contents was a "trade secret" so the manufacturer not only wouldn't tell me what was in it, they also wouldn't tell me if it was harmful.
The other lasted about 15 minutes, Avalanche walked on it to see what it was ... his toenails went right through the 'cover.'
Let's say that I'm not impressed by those mats.

Of my currently three dogs, one will use the raised bad ... the other two just don't seem to see any value in it.

I actually have a couple cooling mats, so worth giving them and the elevated be a try and see from there. Thank you both!