Embedded devices are not generic, they each need their own firmware, specially tailored to their specific hardware quirks, partition maps, firmware formats, GPIO assignments, etc. pp.
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Not that either of those two wireless chipsets would be supported[0] in the first place.
[0] no, I don't consider b43 to be considered "supported" on a 802.11ac capable device.
Thanks for your prompt response. By any chance am I missing something; is this Linksys really not supporter? Perhaps someone 'in the know' knows best. This guy was able to accomplish what I'm trying to do over at ddwrt, using the Asus firmware: https://dfarq.homeip.net/linksys-ea6200-dd-wrt/
But I do not make comparisons, only noting.
EA6200 is not supported. There has been no development to add OpenWrt support other than what you see in the wiki page.
Broadcom devices have very poor OpenWrt wireless support (ie. wifi may be disabled in OpenWrt). Recommend to use DDwrt or Tomato which have better Broadcom wifi compatibility.