Any? https://wiki.postmarketos.org/wiki/Lenovo_IdeaPad_Flex_3_Chr... is dirt cheap and runs PMOS quite well. Actually Chromebooks in general are a good bet when combined with PMOS - or even not combined with PMOS, if you can work with a normal Linux VM on top of ChromeOS.
>>nsonha+qE
You said "ANY arm processor". If you'd like to further constrain the exact requirements, that would be a useful clarification. (Although, I suspect that some Chromebook will still work)