Installing Unity on Linux XFCE Ubuntu 16.04

I am trying to install Unity from the [official Linux build page.](https://forum.unity.com/threads/unity-on-linux-release-notes-and-known-issues.350256/page-2) Unfortunately, I have trouble installing the latest .deb, and the new download assistants, because of my inexperience, are near impossible to run.
**installing the .deb** When I run the usual syntax for installing .deb files (sudo apt-get install unity-editor_amd64-2017.2.0f1.deb), the Terminal returns, among other things, errors: Reading package lists... Done Building dependency tree Reading state information... Done E: Unable to locate package unity-editor_amd64-2017.2.0f1.deb E: Couldn't find any package by glob 'unity-editor_amd64-2017.2.0f1.deb' E: Couldn't find any package by regex 'unity-editor_amd64-2017.2.0f1.deb' } (the /code tag doesn't work for me without that curly bracket at the end. Linux did not return that.)
**Installing through the 2017.3+ download assistants** I have tried installing through the new download assistants, using the installation instructions provided on the "Unity on Linux" forum ([here](https://forum.unity.com/threads/unity-on-linux-release-notes-and-known-issues.350256/page-2))
I run chmod +x ~/Downloads/UnitySetup-2018.2.3f1 and the Terminal returns nothing. I assume it has worked. (also, the check box next to "Allow this file to run as a program" under the Permissions panel in the file browser is filled)
This should, in theory, allow the installer to run, right? Then I run ./UnitySetup-2018.2.3f1 only to receive the error bash: ./UnitySetup-2018.2.3f1: No such file or directory.
-short, frustrated growl-
I have even tried adding -unattended and -install-location! What am I doing wrong?
P.S. Thanks in advance. Bonus points if you tell me the best way to input code-style elements (the /code tag and such)