to be able to play online you must downgrade to awesomenauts 3.2.8 because it's the last version to use steam servers for match making

here are the steps:

1. open your steam library and right click on awesomenauts then click on "properties"



2. Click on "Betas" then next to "beta participation" click on "None" then select "3.2.8 - Steam matchmaking edition"



3. go to awesomenauts and click on install if it didn't start downloading already



4. now you can play awesomenauts 3.2.8 normally from steam




5. it's recommended that you change the matchmaking region in the game settings to worldwide



now you can enjoy Awesomenauts 3.2.8 with working online multiplayer

to find lobbies quickly use Awesomenauts Lobby Browser By Nøkos
this browser can find a list of all current Awesomenauts lobbies including playercount, playerlist and a joinlink.

Link to the Awesomenauts Lobby Browser: https://nautslobbies.com
you only need to click the join link and then click open in steam then the game will start you in the lobby that you picked:

all thanks to jasper for adding the 3.2.8 version to the beta section which made downgrading effortless

and many thanks to Nøkos for creating the lobby browser

Join the Awesomenauts 3.2.8 Community steam group
https://psteamcommunity.yuanyoumao.com/groups/awesomenauts-legacy

Join the Awesomenauts 3.2.8 discord
https://discord.gg/SZud6vPmhM