Hi Jensa,
We’ve arrived at the same conclusion where I work. After experimenting with off the shelf android tablets in one of our products, we were left frustrated that we wouldn’t have a lot of control over the embedded drivers, and that manufacturers would pull them out of production with not a lot of visibility.
We’ve been using Raspberry Pi compute modules in our latest line of products, and that has been working really well for us. If your hardware requirements can be met with what they offer, I’d say go with that.
Otherwise, you can start exploring the i.mx family. A lot of companies offer sodimm-sized system on modules that will happily run their or your own yocto-based linux os.
Regards,
Nicolas