Pinephone exists now, you can buy it today. It runs Linux.
Calls/SMS do work although are not 100% so if you absolutely need these to be reliable you could get a brick phone for like £15 to cover that and then use the Pinephone as a pocket computer. I used it as my only phone for a couple of years and it was mostly fine, now it doesn't have a SIM in it and its perfect as a pocket PC.