You can use any client you like for Mastodon (usually even without logging in, I think that is a server setting) - but by browsing to the instance's domain with

You can use any client you like for Mastodon (usually even without logging in, I think that is a server setting) - but by browsing to the instance's domain with a web browser, you're getting a copy of the latest web client, which may have requirements you don't like or can't fulfill.