Hi,

I'm using a Samsung Galaxy A5 (2015) now with LineageOS... I do not have any idea of your worries or expectations about the size of the phone; it is fine for me. OK, it is way bigger than the n900 (I mean taller and wider) but I can use it with one hand at least and the big screen comes handy...
I have termux on it; I could even wrote a small python script and run it in the background to make some things done... So for me it is quite a good solution for having today's services (browser, navigation, pay/banking) with the capability to costumize (OK, not as deeply as on n900) and even write programs/scripts on it...

OK, it does not have a removable back cover and battery, NFC isn't working and yes, I should use google stuffs but I'm not struggling with ads or anything like that. Or at least you can use this to avoid google...