Where can I download Shimano e-Tube? Di2 Software?

The e-Tube app is available for Windows, iOS and Android. The download links and store pages are:

E-Tube Project Professional (V5), E-Tube Project 4 or E-Tube Project 3.4.5?

With the announcement of the new DURA-ACE R9200 and Ultegra R8100 groupsets, Shimano also launched a new E-Tube Project version - "Professional".

This version is meant to be used by bike mechanics working with bikes on a daily basis. As such, it is not compatible with the SM-BCR2 battery charger or the older SM-PCE1.

If you have an SM-PCE02 then, by all means, use E-Tube Project Professional.

If you're trying to connect to your bike using the SM-BCR2 battery charger or the SM-PCE1 though, you'll need E-Tube Project 3.4.5 or 4.0.4.

I recommend using 3.4.5 if you're using the SM-BCR2 and using 4.0.4 if you have an SM-PCE1. Of course, you can use 4.0.4 with the SM-BCR2, but keep in mind that you may need to use the older E-Tube Project version to update the charger before it'll work with version 4.0.4. You can find versions 3.4.5 and 4.0.4 on the E-Tube Project Archive page.