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Users should consider multi-core, ARM-based (or x86_64/AMD64) devices for mid-range and higher applications.
Purchase of a device with less than 16 MB of flash or less than 128 MB or RAM is unwise at this time (2019).
A device with two, “ath10k” radios should have at least 256 MB of RAM. This eliminates the Asus RT-AC58U, RT-ACRH13, and similar.