(Parts of) Fediverse/lemmy blocked by Sophos firewall?

It seems the Sophos firewall at work blocks all access to lemmy instances.

Join-lemmy.org and lemmy.ml are blocked completely. I can see the front page on sh.itjust.works and lemmy.world, but clicking on a post results in an infinite loading circle. When I try to log in on either site I also get a loading circle on the login button.

Any ideas if I can circumvent the firewall?