"SUNBURST" IT security like a fresh install of Orion?

Yep, got the call right before xmas and was given not many days to get it completed.

CISA put out the advice a week or two back, so that's likely why a lot of customers are following suit:

https://cyber.dhs.gov/ed/21-01/

"Until such time as CISA directs affected entities to rebuild the Windows operating system and reinstall the SolarWinds software package, agencies are prohibited from (re)joining the Windows host OS to the enterprise domain. Affected entities should expect further communications from CISA and await guidance before rebuilding from trusted sources utilizing the latest version of the product available."

There's a lot of information in there, but that seems to be the pertinent bits for a re-intsall.

It should be further clarified that there probably isn't much benefit to a simple re-install if you aren't also building a new machine for Orion.

 I have the same question. Would customers be planning on doing a fresh install on a clean database or a fresh install on an existing database?

Periodic clean installs can improve the performance and security of long-running software installs for many applications, Orion included. Once most customers transitioned apps to VMs, that got a lot easier, especially with the flexibility to test first with a database backup and clean install into a new VM alongside the production server. Note: if you have remote pollers or HA/DR, a smaller clean "lab" install is probably a better choice. You'll put in a bit of time up front configuring a new OS, but the install process can be smoother, because you'll be starting the Orion setup with a clean, fully-OS updated platform.

Take a look at the migration guide here. I've installed and upgraded Orion and it's modules over a hundred times, and still find it helpful because it gets updated to reflect process, requirements and installer changes: 

https://documentation.solarwinds.com/en/Success_Center/orionplatform/Content/Orion_Platform_Migration_Guide.htm 

KMSigma.SWI also has several video how-to's including this one on when you might consider diffrent options. 

https://thwack.solarwinds.com/t5/Announcements-Blogs/THWACK-Tuesday-Tip-Best-Practices-for-Orion-Upgrades/bc-p/614360/highlight/true 

Many have been turning up new servers for a fresh install. Most that I have worked with are using the same DB as well as changing service account passwords for any domain and local accounts used. Especially the local admin accounts used for WPM, if you have the app.