I am trying out OpenWRT with a Linksys E3000, and i found in the hard way that this router have some heavy issues that should be noted in its OpenWRT wiki page https://openwrt.org/toh/linksys/e3000.
The problem i found is if you enable 5Ghz antenna with its available open source driver (the one it comes with the firmware) you can enter in a kernel panic Panic when enabling 5GHz radio on Linksys e3000 (you need to use the other drivers Panic when enabling 5GHz radio on Linksys e3000) and if you by mistake save that configuration you can enter in a crash loop bricking the router Linksys E3000 reboot loop Linksys e3000 debricking help?.
The main issue with that, is also there isn't an easy way to reset the router to the normal state in this case, because anyone of the "soft" options i tested (holding reset, holding WPS button, 30/30/30 https://community.linksys.com/t5/Wireless-Routers/Bricked-E3000-Router-Recovery/m-p/363455#M190728, factory reset https://openwrt.org/docs/guide-user/troubleshooting/failsafe_and_factory_reset, trying to bring the recovery interface https://openwrt.org/toh/linksys/wrt610n#recovery_web_interface, using stock reset www.linksys.com/gb/support-article?articleNum=134969#c) don't do anything useful as they should be (some do something, but you can't reach the router as is described in the steps, as Windows put a weird IP 169.254.234.71 because DHCP isn't working and it should https://forum.archive.openwrt.org/viewtopic.php?id=65390) and maybe the reset is not useful there because it isn't bringing the defaults to the router (i noted after trying to reset the router, the IP range it comes until it reboots alone is 192.168.1.x, and i think, i'm not 100% sure, the last IP range i was using with it was 192.168.99.x).
The only proved options to reset the router in this case is using a serial connector, or making a dangerous short circuit Linksys e3000 debricking help?. I don't have at the moment possibility to do anything of these options, and should be noted in the wiki you can confront this if you have any problem with this router.
The bug about the panic mode is in the issue tracker https://bugs.openwrt.org/index.php?do=details&task_id=1650 but i don't know if it should be useful to post bugs about the "reboot cycle" and the possibility to change something to make possible a successfull factory reset using the router buttons, or making not available the 5Ghz mode with the open source driver in the main releases (for example, with the Huawei HG556a needs to install a driver to use the N mode, the open source can use it, and that info is in the wiki).
Everything of this happens with the lastest release, 19.07.1.
This is for consult how and what add about all this info to the wiki, and later made some research and tests about if there is any possibility to make this router work again without using any hardware option (doubtfully).
PD.: As pointed here Links limit for new users i have edited all links with extra spaces because as new user i only can post two links. Sorry for that.
[Edit tmomas] links fixed