I'm not expert in Linux, but after soooo long I finally found a way to install Adobe Photoshop 6 on Ubuntu 18.04 (Bionic Beaver). Why Adobe Photoshop 6? That's what I got.
Before we continue, I assume you already familiar on how to install application on Ubuntu. Also prepare lot of internet packet data, you'll need it.
1. Install Wine & winetricks
$ sudo apt-get update
$sudo apt-get install wine winetricks
2. Install depencencies for Adobe Photoshop 6
$ winetricks atmlib gdiplus msxml3 msxml6 vcrun2005 vcrun2005sp1 vcrun2008 ie6 fontsmooth-rgb gecko
3. Install Adobe Photoshop 6
$ cd /home/user/path/to/installer
$ wine Set-up.exe
From here and on, the installation process will be the same as when you install Adobe Photoshop 6 on Windows.
Enjoy!