For Beginners - How-to SSH to RPi - Setup Putty in Windows
Use the newest piaware image with this guide:
How to Install and Configure Piaware 5.0 SD card image - Quickstart Guide
I think the stratux dongles already have different device serials, you should just use those instead of changing them.
FR24 can’t handle UAT type messages because their software development department seems pretty lethargic on the feeder site.
I’ve just finished a feed client for UAT/978 for adsbexchange if you like to feed your UAT there: GitHub - wiedehopf/adsbexchange-978: The ADS-B exchange UAT/978 feed client for use with dump978-fa