In the most recent update, the easyanticheat_x64.so got removed. Because of this the anticheat never loads into the game. The easiest way around this is to go back into the old depot and get the preivous file.

https://steamdb.info/depot/1172471/history/?changeid=M:5695517084385880277

Easiest way to do this is using a tool called DepotDownloader. https://github.com/SteamRE/DepotDownloader

This is in the AUR depotdownloader-git. It required dotnet 6

Then run this command in the base directory of apex legends /SteamLibrary/steamapps/common/Apex Legends/

echo "easyanticheat_x64.so" > list.txt && depotdownloader -app 1172470 -os Windows -depot 1172471 -manifest 5695517084385880277 -user "USERNAME" -password "PASSWORD" -filelist list.txt -dir . && rm list.txt