Step by Step Guide

Step 1:

Download version of Adium you need: https://www.adium.im/, and drop the app from the .dmg image to your Applications folder.

Step 2:

Launch Adium.

If everything is good so far you should get this window:

Step 3:

Click on Continue, and on the other screen select IRC from the Service drop-down menu.

Enter username of your choice, I recommend, you enter your Discord username, and then enter password of your choice too. Don't enter your Discord password. (Never use same passwords for multiple accounts.)

Step 4:

Hit Continue again, this should pop up. Enter address: chat.macintoshgarden.org, then click on Connect.

Step 5:

You should get this screen:

Now let's dive into the command stuff.

First of all, type command: register (password). The password must be the same as the you typed in the Step 3. You should receive a message: "Account successfully created"

Step 6:

Relaunch Adium.

Step 7:

Now you must add your Discord account to your BitlBee profile, to do that type: account add discord yourmail@email.com yourdispassword. You should get a message saying: "Account successfully added with tag discord" If you have 2FA enabled, go to your inbox and confirm the new login location.

Step 8:

Relaunch Adium.

Step 9:

Now the Discord account should be succesfully added to your BitlBee profile.

Step 10:

Now to list your chats type: chat list discord. You should get a list of your chats. To send message to channel of your choice you must select and join the channel. To do this type: chat add discord !(number of the channel from the list). When it's successful it gives you a message: "Chatroom successfully added, join with /join #Tst.test" To join and start typing, click on the hashtag, a new tab should pop up in Adium named after the channel. Click on it, and start typing. Congratulations! You can now chat with others on Discord with your Vintage Mac.
Thank you, if you find this guide useful. Have a nice day!