I don’t have a compatible OS on my PC; working explicitly from an android phone. Is there any way to get established as a user with just the android app?
With reference to signing up for the service, I would assume that you are referring to sign up as a user to a mattermost team via an invite link and fully utilizing the mobile client for messaging. For example:
It should be possible to just utilize the Android client to manage your conversation and settings there. Nevertheless, I would like to know the OS that you are using on your PC. Is it not included in the list here?
Additionally, have you also considered using the browser client?