virtualbox.org

I created a Virtual Machine (Ubuntu Desktop guest on Windows 10 host) that contains my "daydream" and "ready to go" development environment (code editor, git, package managers and so on...). I'ld like (in some way, if it's possible) bring it always with me (I work on different PCs and places) in a external SSD drive and run it on other PCs (whether they are Windows or Linux host, is it possible?) just plug in the drive and run.

Is it possible? What's the fastest way to use a VM on external drive among different PCs?

You can do that, but you will have to install Virtualbox on each host PC. USB3 would be best for highest drive bandwidth. Also, Windows hosts can change the drive letter of the external drive, which would prevent your guests from starting. You should learn how to change the drive letter back to what it was, then the guests will start. If you set the drive letter higher in the alphabet the chances of a letter change are reduced.
Unplugging the external drive while the guests are running will be bad for the guests, to say the least.
Oh, one other thing. On a Windows 7 host I had trouble getting a guest on a USB drive to run unless I right-clicked the Virtualbox GUI icon and clicked "Run As Administrator". viewtopic.php?f=2&t=38007