Take a look at <https://www.gl-inet.com/>. These boxes come with a nice, simplified GUI, but will run stock OpenWRT, which you can build yourself if you wish.

I placed one of these boxes behind my ADSL router to do load-balancing. To use it as an Internet router, you'd instead need to couple it with a modem. A colleague whom I trust recommends Draytek kit but (a) I've not tried it, (b) it's not cheap and (c) I'm just a stranger on the Internet, so read around carefully before splashing out.