not an expert by any means on this, but I've worked before with the Khadas VIM boards, which are development boards where you can install Android and start developing your project. The advantage of those is that they use Amlogic chips which are very affordable and come pretty much ready as product from Alibaba (search for "android box" and you'll find a bunch of white-label board/cases that are ready to be used)
Alternatively, if yoou want more control/performance than what Android gives you, you can also look into Buildroot, which makes it very easy to build a custom linux distribution with your application in it, that is, you get a firmware ready to burn in your board with linux and your app running in it.
Alternatively, if yoou want more control/performance than what Android gives you, you can also look into Buildroot, which makes it very easy to build a custom linux distribution with your application in it, that is, you get a firmware ready to burn in your board with linux and your app running in it.
Good luck!