How to re-download Lightroom 6?

Keep in mind that LR6 is outdated software, almost 8 years old. Given how often people upgrade computers, operating systems and camera equipment, it may not be a practical fit for you anymore.

When you're ready, a Photography Plan bundle is your best option.

Creative Cloud Photography Plan (approx $10/month for 12 months). Includes the following:

• Photoshop CC and Photoshop on iPad,
• Camera Raw,
• Lightroom on desktop, mobile and the web,
• Lightroom Classic (similar to LR6),
• Portfolio website + hosting,
• Adobe Express (free starter plan),
• Bridge,
• 20 GB cloud storage (upgradable to 1 TB).
• Free updates & upgrades for as long as you subscribe.

https://www.adobe.com/creativecloud/photography.html

See System Requirements:

- https://helpx.adobe.com/creative-cloud/system-requirements.html
- https://helpx.adobe.com/photoshop/system-requirements.html
- https://helpx.adobe.com/photoshop/kb/photoshop-cc-gpu-card-faq.html

Hope that helps.

Computer crashes happen... the FIRST time you download a program make an external copy

IF/When you do have a download, be sure to copy it to AT LEAST one external device
-you should ALWAYS keep a copy (or two!) on an external device
-since Adobe DOES SOMETIMES REMOVE OLD VERSIONS FROM THE SERVER
-a usb flash drive or external hard drive, or write to a CD or DVD
-plus a text file containing your serial number if you have a serial number program

Here you'll find the appropriate download links

Adobe Lightroom 6 (CC 2015) Direct Download Links – Free Trials | ProDesignTools

Scroll down to the section "Adobe Lightroom 6/CC 2015 Direct Download Links"

Save the installation file for further usage. It's not sure how long tihs files will be available.