As mentioned in the comments, some Android phones will come close, especially if you root/modify them afterwards. There is an alternative that has not been mentioned, from the Mozilla organization: Firefox OS.
I have only used one of these phones briefly (for a couple of hours) personally, but I know others have used them successfully and enjoyed the open ...
It's hard to find a fully libre design in your price range. Most will be based on Allwiner or similar SoCs, which are probably not vendors you want to support, regardless of the availability of opensource code, not to mention schematics. In addition you probably won't find WiFi without closed, binary blob firmware.
Having said that, there are such vendors ...
Minifree offers the Libre WNDR3800 Router.
These are refurbished Netgear WNDR3800 or WNDR3800-1CHNAS routers that come pre-installed with free software only (uboot, libreCMC).
While it has no RYF certification as of 2019-01-08, Minifree submitted the router for approval:
It’s a completely FSF-endorseable router: in fact, Minifree has sent the FSF a ...
I recommend the Pi-Top. It is mostly opensourced. The GPU driver has a proprietary blob in it, I think, but of course you don't need to install that; there are several terminal-only distros you could use on this device. I believe even most of the hardware, if not all of the hardware, is open source at this point, or will be in the near future.
You should get a Nook.
There are several variances to the Nook e-reader - mainly it's between the Simple Touch, Simple Touch with GlowLight, and now GlowLight Plus. Basically it whether you want a backlight or not or you want refurbed or new.
Let's see how it stacks up with your requirements:
Everything FOSS. Moot point. Every ereader comes with built ...
The best you can get, (which you can't get, because it's not released for the general public yet), is the BeagleV. This board has a RISC-V CPU. It does come with some nvidia hardware on it, but the rest should be good.
It is supposed to be available for the general public around summer 2021, where you will be able to get cheaper options than the current, ...
There are two tablets which are officially supported by Replicant - a fully open source Android distribution - namely Galaxy Tab 2 10.1" and Galaxy Tab 2 7.0". However, they run on proprietary hardware and firmware.
Another possibility is an open source LuneOS Linux distribution, which runs on HP Touchpad. But it has proprietary hardware as well.
We will ...
If you are willing to wait - there is the Purism Librem 5 which uses a CPU with fully available documentation, and a GNU/Linux distribution by the manufacturer (Debian-based). Current ETA is Q3 2019.
The only snag you might hit (which is basically unavoidable AFAIK) is the modem firmware.