Terrace ceramic tiles in gravel - Any experience?

But you can't hear any other opinion, can you? I spoke with a master tiler at Raab Karcher, he said gluing would be the last option, gravel wouldn't be a problem at all,

well, I have the experience right here at my door. I have already lifted and re-laid them once. And that's why I put the slab on supports and no longer used joint sand.

In the past, the slabs were always laid in gravel, I don't know why everyone wants to glue them now.

Because the slabs used to be 5cm or more. 2cm is a modern thing. In the past, they were concrete slabs (which are still quite common today and also usually NOT glued at all).

Ok I can tell you quite precisely how it is with the 2cm ceramic slabs on the gravel:

We explicitly wanted 2cm ceramic slabs selected by us to be laid as a terrace because of the appearance.

- Buyer says in gravel no problem.
- Gardeners all say: never on gravel – only on concrete.
- Gardener we trust told him to offer us the slab on concrete – he says he does it on gravel because due to the size and weight 60×120 gravel is unproblematic. Only smaller slabs are bad.

- Now they are lying there, on the gravel, and after three months of little use the first ones already wobble when walking over them, not bad but still not nice....
GD

I just looked at rectangular terrace slabs again, they cost so much more that it’s not worth it to me, I’ll stick with the 80 by 80 format because they are very nice, or rather I like the pattern.

So for laying: we want it to be fixed as well:

Seal the soil
Gravel 30cm? seal
Splitt?
and then mortar/concrete cement?
then the tile with adhesive

I would also like to have a foil laid against [U kraut]. It also has to be fitted in between.

All right, you convinced me. I will have it laid in mortar. Could you please help me a bit with the selection:

80 by 80 Villeroy & Boch I can get cheaply, price not yet certain, 120-23 Euro...m2

I don't find 120 per sqm cheap at all but rather quite expensive. And Villeroy & Boch, I don't know if I would want that as a terrace slab... they already annoy me enough in the bathroom...

Go to a proper, exclusive tile and slab store. We were in the fancy tile store in town and ended up
< 70 per sqm for 120x60 for our desired terrace slab.
Alternatively, a tiler who can also order terrace slabs for you.
GD

I would also like to have a foil laid against weeds. It must also fit in between.

What nonsense. You make a layer of drainage concrete – there is no need for protection against weeds. They do not grow through concrete (and certainly not through the tiles). And what do you mean by "seal"? Never heard that in this context.