pawb.fun is one of the many independent Mastodon servers you can use to participate in the fediverse.
This instance aimed at any and all within the furry fandom, though anyone is welcome! We're friendly towards members of the LGBTQ+ community and aiming to offer a safe space for our users.
@deetwenty@charlotte Relm4 looks interesting for something GTK-4 based, but truly cross platform apps would want to go for something less linux-centric probably