WiFi is poor in the house despite a repeater, what to do?

We have a Fritzbox 7490, which is not sufficient for the whole house, especially not through 20 cm concrete ceilings. I supplemented it with a Ubiquiti access point, which works quite well.

Actually, that should work without a repeater or access point or anything else. A normal good router should manage it

No, it doesn't have to. With plenty of steel in the ceilings, that's it for reception. I have one from Fritz, it's good. We have two Fritzboxes and a repeater, and like that mesh LAN and DECT throughout the whole house. Great.

The other way around with us: the router is under the roof (2nd floor). Reception is already weak on the 1st floor and none in the ground floor.

Therefore, the Fritz Repeater 1750e (configured as an Access Point) is connected to the LAN socket on the ground floor.

Well, all I can do is advise everyone to throw away (or sell) all those repeaters and set up a proper network with access points on every floor. If it really is that bad and you depend on Wi-Fi.

My Fritz in the HAR manages to provide Wi-Fi to all floors and even reaches the surrounding neighbors. But yes, there are spots here and there where the reception is also disturbed, but these are in the roof box, etc., meaning they are not worth mentioning since nobody needs Wi-Fi there anyway.

We initially had only a Fritzbox in the utility room on the ground floor in a timber-framed house. The Wi-Fi on the upper floor on the other gable side was very lousy in the 5G network... Fortunately, I had planned a LAN ceiling outlet each on the ground floor and upper floor. Now, as planned, 2 UniFi Nano HDs are hanging there and it works great. When changing floors, my phone is automatically handed over from one access point to the other access point.

I have a 2nd FB on the other floor that has the same network name. So you connect to the same network on different floors.