It varies from device to device but you might be surprised to know that many of the features you've listed often do not require a binary driver or loadable firmware. They are often supported by the kernel which is of course open source. When I run Debian or Devuan on my N900, the only binary blob I need to use is the loadable firmware for wireless network connectivity. WiFi is a frequently problem on many devices but Replicant offers connectivity via an external Wi-Fi dongle as an alternative to binary blobs for certain devices. This could probably be done on the N900 too once USB host mode has been mainlined. Have a look at the Replicant status page for what features work on which devices. It does not explicitly mention the display or touchscreen input but one would presume they are provided by the kernel.

I'm not endorsing nor saying that anyone should go out and use Replicant. A Maru OS chroot on Android solves most of the problems you have listed. It's not ideal and it's not native but if the main objective is to run GNU/Linux on a plethora of Android devices (the same objective as Halium), then it does a bloody good job at that. If we embrace Android crapness such as planned device obsolescence, insecure devices, etc., as Halium does, what is it exactly that this community stands for?