Hey there Jerry,
Awesome to hear you're still setting up projects for generations to come! :-)
In order to play TBC (v2.4.3), you'll need MaNGOS One. A guide to installing it on Ubuntu 20.04, as far as I can see (in the guide section), is not available.
However, a guide for Ubuntu 21.04 may* suffice, which is found here: https://www.getmangos.eu/wiki/documentation/installation-guides/guideslinux/m2-setup-on-ubuntu-2104-r40013/
The only things you need to do differently from that guide is step 2, as followed:
mkdir ~/mangos/
mkdir ~/mangos/db
cd ~/mangos/db/
mysql
CREATE USER 'mangos'@'localhost' IDENTIFIED BY 'mangos';
GRANT ALL PRIVILEGES ON *.* TO 'mangos'@'localhost' WITH GRANT OPTION;
exit;
git clone https://github.com/mangosone/database.git --recursive
cd database
./InstallDatabases.sh
And step 4, as followed:
cd ~/mangos
git clone https://github.com/mangosone/server.git --recursive
cmake -S ~/mangos/server/ -B ~/mangos/build/
cd ~/mangos/build
make -j<# of CPUs/Cores>
make -j<# of CPUs/Cores> install
In case you want to utilize screen (highly recommended) as mentioned in step 7, you might also have to install it first using:
sudo apt-get install screen
The rest of the steps should just be followed as written, although I've been out of the MaNGOS scene for a while as well, so take my 'knowledge' with a grain of salt.
Hope this helps you out a bit!
Note: I haven't tried MaNGOS One on Ubuntu 20.04 yet, currently in the progress of getting MaNGOS Zero up and running, but the process seems pretty much similar.
* Unless 21.04 and 20.04 vastly differ in packages and whatnot, someone ought to confirm this, along with the rest of the things I wrote.
EDIT: Guide works, although it being a bit wonky here and there, may write one myself soon (read: one day).