Most Freenode channels have since moved to libera.

I'll make a show about why and a show about how to connect to libera, but here's the spoiler:

https://kparal.wordpress.com/2021/06/01/connecting-to-libera-chat-through-matrix/

 - Instead of #freenode_#oggcastplanet:matrix.org use #oggcastplanet:libera.chat (yes, they have their own gateway!)
 - Instead of chatting with @appservice-irc:matrix.org to store your login and password, chat with @appservice:libera.chat