Beyond the article being ancient at this point (in terms of AOSP and Android development lifetime), Stallman's argument boils down to the same talking points of Free Software purism.

To the first real point being transformed here: Android is not GNU/Linux because it does not contain much of the GNU Project's software. While it's correct to claim it's not GNU/Linux, how does it not make it Linux still? Is Alpine Linux not considered "Linux" because it doesn't contain GNU? Please elaborate on this point of Linux being Linux because it has GNU.

To the second point of including proprietary drivers, firmware, and appplications: we once again meet the questionable argument of transforming an OS to something else. Points are made that Android doesn't fit the GNU ideals due to its usage and inclusion of proprietary kernel modules, firmware, and userland applications. These are valid points to be made in that these additions muddy the aspect of Android (as packaged by Google and major smartphone manufacturers) being truly free software. However the same can be said about traditional "GNU/Linux distributions". Any device running on x86 (Intel, AMD) will be subject to needing proprietary firmware in order to function with that firmware having a higher control level than the kernel itself, just as Android would. There is also the note that while it is less necessary now to have a functioning desktop, a good portion of hardware (NVidia, Broadcom, Intel, etc.) require proprietary kernel modules and/or userland drivers in order to have full functionality that the average user may want. Finally, there is proprietary applications as well. Some Linux desktops include proprietary applications like Spotify, Steam, Google Chrome by default. Are we really to also exclude an overwhelming majority of the biggest Linux distros as Linux as well being that they include proprietary software or rely on proprietary code in some fashion? GNU itself lists very few distros as GNU-approved.

To note, AOSP does have a different userland environment than your standard Linux distro running X11 or Wayland. That is by far the best reason I could think of to classify Android as a different category of 'Linux' from say Debian, Fedora, OpenSUSE, Arch, Gentoo, Slackware, and others. However, AOSP is still capable of running with no proprietary userland software and can even be made to still run cli applications as well as run an X11 server that is capable of launching familiar desktop Linux applications. I really think that the arbitrary exclusion of Android from being Linux by virtue that RMS doesn't think it fits with GNU ideals is silly. If there are better arguments to be said for why Android (especially AOSP) shouldn't be seen as Linux with a different userland ecosystem rather than not Linux entirely, I'd love to see them. However, I remain unconvinced so far.