@Hughenknubbel just pointed me to Sengi - a Mastodon/Pleroma web client for the desktop. What is particularly interesting is that multiple accounts are supported in parallel.
And one thing is rather unusual in terms of operation: to change the account, you have to select it with a right-click.
@sengi_app that's a rather unusual decision. Intuitively, most people would probably just left-click on the account icon. Is there a special reason why a right click should be made?