Edit: Drivers for GigaDevice and Paragon SPI-NAND accepted upstream. Since this thread started, I broke down and bought myself an AR300M. As a result, both devices are supported by the PR shown below.
Having an AR750S running GL.iNet v3 firmware through two weeks of travel made the mess of hotel wireless and VPN so much easier to deal with. If you’ve got the latest GL.iNet firmware running, unless you’re a developer, I’d stick with that for daily use.
Initial support for the AR750S (“Slate”) on the ath79 platform, Linux kernel 4.19, with the upstream SPI NAND framework has been submitted to OpenWrt. Current patch series is available at OpenWrt development - Patchwork
Note that these patches are subject to review and revision.
These patches, applied to OpenWrt
master, should provide images suitable for both sysupgrade from both NOR and NAND and U-Boot flashing through the usual OpenWrt build process.
The above patch set includes mtd: spinand: Add support for GigaDevice GD5F1GQ4UFxxG, in upstream (Linux) review at this time.
I can’t comment on when/if these will be accepted into either the OpenWrt project
or the Linux project. As I don’t have an AR300M in hand, I don’t know what NAND is inside of it, so can’t easily know if it will be as straightforward to add as I hope to that it will be.