I just downloaded the most recent mainline image for the NanoPi Neo (Ubuntu_xenial_dev_nightly.7z). It boots and runs fine. However, I was trying to access the UART1 on /dev/ttyS1, but apparently it is not enabled by default.
The dmesg output is:

dmesg | grep tty
[    0.000000] Kernel command line: root=UUID=d9678417-38b4-4c2b-993e-04cdea0247de rootwait rootfstype=ext4 console=tty1 console=ttyS0,115200 hdmi.audio=EDID:0 disp.screen0_output_mode=1920x1080p60 panic=10 consoleblank=0 loglevel=1 ubootpart=eeb8ef06-01 ubootsource=mmc   sunxi_ve_mem_reserve=0 sunxi_g2d_mem_reserve=0 sunxi_fb_mem_reserve=16 cgroup_enable=memory swapaccount=1
[    0.000973] console [tty1] enabled
[    4.066624] console [ttyS0] disabled
[    4.086857] 1c28000.serial: ttyS0 at MMIO 0x1c28000 (irq = 33, base_baud = 1500000) is a U6_16550A
[    4.086926] console [ttyS0] enabled
[    4.111551] 1c28c00.serial: ttyS3 at MMIO 0x1c28c00 (irq = 34, base_baud = 1500000) is a U6_16550A

I can see that ttyS0 and ttyS3 gets initialized, but I don't see anything related to ttyS1 or ttyS2. By using setserial I can see that ttyS0 is attached to interrupt 33, but ttyS1 and ttyS2 are attached to interrupt 0 (which probably means none). I tried using minicom to talk over ttyS1 and ttyS2. It can open the port, but nothing goes through it. I was using ttyS1 before with the legacy Armbian image, and it was working fine. By updating it to the most recent ubuntu xenial it stopped working. I know this is a nightly build and is not supposed to work perfectly, but I really want to use this updated version because it runs on a more recent kernel.

Any ideas on how to fix this?

Thanks!

https://docs.armbian.com/Hardware_Allwinner_overlays/