>Windows
1. Server browser, autodownloads source port and wads:
https://doomseeker.drdteam.org/
2. Inside doomseeker config options>configure>file paths check the folder/directory it's searching for wads and add whatever folders you want. Don't forget to press apply/okay.
3. Unzip this (contains doom2.wad) inside one of the folders you have configured (DOOM2.WAD): https://u.pone.rs/lmhqhawo.zip
And (You)'re all set to play.

>Mac OSX
1. https://zandronum.com/download
2. Follow windows steps starting from step 2.

>Linux
1. flatpak install flathub com.zandronum.Zandronum
2. Follow windows steps starting from step 2.

>MIDI
short midi soft synth guide if you don't like the sound of OPL (Check in ESC>Sound Options>MIDI Device. What and select something that isn't FMOD since that doesn't work):
https://rentry.org/vueh2y55

>Linux extras (if you aren't using the flatpak)
>I HATE FLATPAKS!
Get doomseeker from your distro repos or build it yourself:
https://doomseeker.drdteam.org/download.php
>I'm getting a missing lib error!
jpeg libs download:
https://u.pone.rs/lrlbqptv.zip
Create a shell script
#!/usr/bin/env sh
LD_LIBRARY_PATH=/path/to/jpeg_lib /path/to/zandronum
>I still get the error when i try to join alpha/beta servers
Try to enter the server, doomseeker will download the correct version.
check doomseeker menu options>zandronum>"Directory for testing releases"
That's the path were your downloaded testing releases are. Modify the relevant shell script and add to the LD_LIBRARY_PATH line like this:
export LD_LIBRARY_PATH=.:$LD_LIBRARY_PATH:/path/to/jpeg_lib
jpeg libs download: 
https://u.pone.rs/lrlbqptv.zip
>BUT I LIKE NIX(OS) ANON
doomseeker is on nixpkgs. Zandronum stable is in nixpkgs but you will build from source
Expressions for zandronum binaries (including alpha release). Add to your package overlay:
https://u.pone.rs/emuligtp.zip
Update source url and hash if you need to. Copy paste and modify for more versions. If you have multiple versions on a package list, you need to use (lib.hiPrio zandronum-bin) one of the packages. When joining a testing release server, let doomseeker autodownload for you, then replace the shell script at the testing releases directory (check path in doomseeker menu options>zandronum>"Directory for testing releases") with a relative symlink to the relevant zandronum binary. Example:
mv 3.3-alpha-r251208-0355.sh 3.3-alpha-r251208-0355.sh.bak
ln -sr $(which zandronum-alpha-bin) /home/anon/.local/share/doomseeker/plugins/za
ndronum/3.3-alpha-r251208-0355.sh