https://zaufanatrzeciastrona.pl/post/o-trzech-takich-co-zhakowali-prawdziwy-pociag-a-nawet-30-pociagow/
https://xonotic.org/
I asked admin of my instance few minutes ago and didn't get reply yet, but it seems your instance(mastodon.sdf.org) blocks pone.social.
EDIT: my instance isn't blocking mastodon.sdf.org
@uis
@lemmy.world