There are also lots of cheaper SoMs if you're not allergic to Chinese chipsets, and the cheaper ones tend to have PoP on-package DDR so you can spin your own 4-layer PCB without having to pull your hair out impedance matching DDR3+ traces. That, of course, if you can fit into ~64MB RAM.

> The kernel contributions are also a bit on the shakier side which requires spending expensive developer time to deal with kernel

NXP/i.MX are way better at mainline kernel than Broadcom that RPi is based on, come on.. and they have cheaper options like i.MX 9 series. Other vendors, yes, mainline support could be pretty spotty.