I’m interested in getting an inexpensive device to install PostmarketOS on just to play around with mobile Linux and maybe do some testing (I’m not expecting this to be my daily driver phone).
The Samsung A5 seems like a device that works reasonably well with PM and can be bought on Ebay fairly cheaply. However, it looks like most of the A5 I see on Ebay are 2016 and 2017 models. I notice the Wiki specifically mentions the 2015 model though.
Are these devices compatible, or do I need specifically the 2015 model?
Any other suggestions for inexpensive mobile devices that support PM that are widely available?
They are not compatible, samsung for some reason likes to release completely different phones with almost identical names. The 2016 and 2017 models are somewhat supported by postmarketos, see wiki pages for Samsung Galaxy A5 2016 (samsung-a5xelte) and Samsung Galaxy A5 2017 (samsung-a5y17lte), but way less features work compared to for samsung-a5 2015.
An alternative could be samsung galaxy s3, modem and camera does not work, but apart from that it is pretty usable.