Update on my “issue”: I used the Fairphone 5 for some time now and got used to it after all.
- The not that-well-fitting bumper is okay. It did not come off so far at least and started to ignore the tiny loosening on the upper right edge.
- The bigger screen and the thicker device is okay as well. I got used to it.
- The rounded corners still bug me a little, but in the end it’s not that of a problem. Many apps do not use the full height anyway, which makes the screen lock squared in most situations anyway.
- Unlocking my device with double tap: I just do not use it, but is still a bit sad that it does not work that well.
- Pinch zoom out Nova launcher gesture: this still bugs me often times, but luckily the pinch zoom in gesture does work better. I use this more often than the other one, luckily.
- Enabling the flashlight: on the Shift6mq it is possible to enable / disable the flashlight by holding the power button, when the device is locked. I would still love it on the FP5 as well. But in the end it can be enabled / disabled with the drawer quite okayish-quickly as well. So this is okay as well.
Overall: for now the FP5 feels more performant. Seems like I will keep this one and sell the Shift6mq to a friend.
Thanks for all your replies here!