I bought this AR300M model, with 128MB NAND flash.
I'm trying to build a custom kernel following the instructions here.
However, "Target Profile" only offers AR300M-Lite and AR300M-16 (16MB NOR Flash). No option for AR300M-128.
What options should I pick? I'm guessing I should choose "Generic devices with NAND flash" under "Subtarget", but then what do I pick for "Target Profile"?
As of 19.7.* it's under the AR71XX target, not ATH79. No idea about master, but that might be the case as well.
NAND flash is only supported in ath79/nand for after 19.07.
ie You will currently find it only in snapshot.
I would rather not use snapshot... What are my options for using 19.07.3 on it?
19.07.3 does not support nand on the ar300m.
You can flash the nor firmware with 19.07.3 but will have to set bootcount=3 in the existing nand firmware environment otherwise it will boot from the manufacturer's nand firmware rather than your nor firmware.
From what you're saying, does that mean the bootloader is going to remain in the NAND flash?
I'm installing openwrt in order to not rely on proprietary software, so I'd rather not use the preinstalled bootloader if possible.
Also, does the NAND version keep the 16MB NOR flash?
The bootloader is u-boot and I am pretty sure, resides in the NOR flash. All models of the ar300m have NOR. Some have NAND as well.
Those that have NAND try to boot from NAND first then fall back to NOR.
You can build your own u-boot and flash that, but that is nothing directly to do with OpenWrt and would require detailed knowledge of the flash layout. It has been done - but not by me. Hard bricking is probably quite easy to achieve