Shower tray longer than 140 cm: Save the door because of that?

you can also feel cold in open showers because of the steam column.

What do you mean by "steam column"? A specific shower head? Or a draft caused by the showering?

We have planned 1.60 x 1 m and according to the experiences of acquaintances there should only be a few drops left at the edges. A coworker told me that they have 1.5 x 0.90 and nothing splashes out there.

Maybe it also depends on how much one moves around in the shower and how far the water goes additionally :D

Yes, I discovered this after Halloween.. I prefer green to red ;) … color!

Since the floor down there is sloped with filler, at least the side walls at the bottom would have to be either sloped or the floor would have to be elaborately "folded."
Yes.

Neither the floor needs to be sloped with filler nor the side walls at the bottom sloped nor anything elaborately folded.
In new construction, the screed is poured slightly sloping towards the drain from the start. At the edge between the sloped and straight floor, the tiler applies a specially suitable sloped metal strip for this purpose. And the glass wall is placed directly on the edge, that is, on the straight floor right next to the slope.
So this works perfectly fine with a glass wall or even several glass walls.

At the edge between the slanted and flat floor, the tiler installs a specially suitable slanted metal strip for that purpose.

Yes, but not cost-neutral. The OP is looking for a solution that might

Also pays off financially

be more cost-neutral. And this solution is not.

Why shouldn't that be cost-neutral? With [Flliesenboden], without a shower tray, you have more freedom in the size design of the shower room.

Why shouldn't it be cost-neutral? With tiled floors, without a shower tray, you have more freedom in the size design of the shower area.

Because there are always costs involved when you have to build a boxed-in area within a room (screed layer) and then plaster over it (tiler). They charge well for that. Why? Ask the craftsmen… Every stroke costs extra.