Screed in garage - how to seal the edge joint?

I don’t fundamentally doubt that, but it surprises me.
As I understand it, a screed slab can expand, press against the walls, and thus cause damage. Why is that different in a garage than in living spaces?

Well, quite a few things are being, to put it simply, mixed together here.
On the one hand, in residential construction, at least in Germany, we always deal with screeds on insulation layers. These are the so-called "floating screeds." Because they are applied on insulation layers, they require an edge joint so that the impact sound insulation layer can perform its function and also so that no sound bridges are created.
The second are heated screeds in residential construction.
These also require edge joints for the aforementioned sound insulation reasons, but also because they undergo length changes due to thermal expansion.
In the case in question here, however, we are talking about a screed in a garage.
Here, the screed has to withstand higher forces from vehicle traffic than in residential construction, impact sound insulation plays no role, and thermal insulation usually doesn’t either.
This means that the screed can be installed - unlike those in residential construction - bonded to the concrete surface and in a smaller thickness (25-35mm).
And since it is firmly connected to the slab, such a screed does not move.
Which is why an edge joint would be nonsense.
Incidentally, thermal expansion of a cement-bound component is only really relevant in heated screeds. Normally, joints of 10mm width are introduced purely for safety reasons - and this width is also completely sufficient to avoid sound bridges at, for example, rising walls despite length expansion.
Therefore, my answer already gives the correct indication!
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Regards: KlaRa

thank you for the detailed explanation. Especially that a garage screed - unlike one in the living room - is not heated, is clear to me. :cool:

I also have a screed with a joint and sealed it with acrylic in the form of a cove. Then applied an epoxy coating twice on the floor and pulled it up 10cm on the wall. Whether it is professionally done can be discussed, but it has held for years without cracking or anything like that.