Hi @Michielt, just to confirm: If you use the downloaded minimal reference image and make the changes in the device tree, do you get the builtin UART’s working?
I just read your answer and saw that you want to build a debian image. In this case I would suggest to you that you take a look into Torizon, as it provides easy to use images where you can load your application using containers that are based on Debian images.
Then I saw that you already asked about that on this question:
If you cannot use Torizon because of the lack of modules but you would otherwise be interested in trying it out you could build your own Torizon Core image and include your customized kernel configuration.
If you don’t need anything debian specific for your application, then you can also build the kernel yourself by following this article and also customize your own image to load your application and libraries.
If you need help with customizing OS images for your application, we also have in our partner network a list of several companies that can help you.
Building a custom debian to run on a platform that’s not supported by them is not that simple. It should be doable if you are able to pick all the correct pieces (kernel image, binary firmwares, kernel modules) that are provided inside the yocto built image and load them on your image. As you already noticed by your tests, if something is missing or is from an incompatible version / build stuff stops working, you start to see kernel panics and can run into other stability problems.
Also it is worth to mention that setting up a builder system that can actually replicate your debian image for maintainability in the future can also be a pain.