I have started looking for my next router, and I love the hardware on the RB493G. However, OpenWrt is the only firmware I will consider using. It looks like this beauty is as close as it gets to openwrt support except for one hitch, the flash chip.

Check this thread:
https://forum.openwrt.org/viewtopic.php?id=32931
with reference to this post:
https://forum.openwrt.org/viewtopic.php ... 42#p147242

Is this correct? Are there two different flash chips on these boards with no telling which one I am getting if I order? Does one of them need special linux patches to behave? If so, where are the patches?

All pointers are greatly appreciated

Did some more digging and found the bug-report, it is here:
https://dev.openwrt.org/ticket/10272

Looks to me like it should be fixable, and I believe it is in Mikrotik's interest to have a patch submitted. Posting it on the issue tracker linked above may be sufficient to have it included upstream in linux.