I just installed Manjaro minimal (headless) on a Raspberry Pi 3B which is running fine and stable.
One thing that confuses me is the following questions during updates (pacman): Replace rpi-eeprom with extra/rpi4-eeprom? What puzzles me is that this mentions a Pi4 whereas I’m on a Pi3. So far I rejected this update.
Does anyone have an idea if I should install this upgrade (ignoring the difference of the PI model)?
I’m not sure how you got into that situation. rpi-eeprom should not have been installed in the first place. It is supposed to be a user elective package. You only flash the pi4’s and pi5 eeproms. The other pi devices uses bootcode.bin. Remove the rpi-eeprom package if you are only going to boot the pi3 in the image.
Thanks for your quick reply 
This is a blank, fresh installation (from manjaro.org → downloads → Raspberry Pi) - I just installed it on a few RPi3, only went through the initial config script (started automatically) and then did a first upgrade (pacman -Syu). That’s all I did so far, no other manual change and it happened on each of the Raspberry Pis.
Additional question - what is the best way to remove the package (simply via pacman)?
Yes - pacman is the native package manager.
Those are outdated - february 2023.
Possibly better to use from the github repo or prepare the sd card using manjaro-arm-installer script.
git clone https://gitlab.manjaro.org/manjaro-arm/applications/manjaro-arm-installer.git
Ensure you meet the dependencies described at manjaro-arm / applications / manjaro-arm-installer · GitLab
Then run the script - recommended to point to unstable branch
If running on the x86_64 version of Manjaro - be sure to restart systemd-binfmt as described
sudo systemctl restart systemd-binfmt
cd manjaro-arm-installer
sudo bash manjaro-arm-installer arm-unstable