On another account I was once informed by a fedizen(fediverse citizen?) that there is a social media platform that is sort of "independent" from the ActivityPub protocol. That ActivityPub can be turned off and on at will or something like that.
Sounded interesting but at the time I was not ready to try new things so it remains a mystery to me to this day.
I'm not exactly searching for a "Mastodon Alternative" but somethiing that complements

People building the future of the social web—interoperable and decentralized—need to protect themselves against copyright liability. This post gives an overview of the steps to take. It’s meant for operators of Mastodon and other ActivityPub servers, Bluesky hosts, RSS mirrors, and other decentralized social media protocols, and developers of apps for those protocols—but it will apply to other hosts as well.

The Sovereign Tech Agency, commissioned by Germany's Federal Ministry for Economic Affairs and Climate Action, has awarded hundreds of thousands of Euros to Mastodon to address key infrastructure challenges faced within the fediverse ecosystem.