I can only speak for myself but my Samsung has not given me any problems expect when I installed /e/ but that was more the problem with samsung the company making things very difficult.
But other than installing it works flawless.
My FP4 worked flawless until v.1 which flaws will probably be fixed in v1.1. Im honestly pretty happy with everything so far.
I also use a GS290 and am very satisfied with this smartphone. Unfortunately, the camera leaves a little to be desired. For this reason, I have already asked to support the gigaset successor GS5 with /e/OS. In this device, the camera is much better and the battery can be changed. Maybe you would leave your support for the GS5 in the following thread. The more people decide for this device, the more likely a support will be.