Ten64 User Manual
ten64doc.traverse.com.au
Key pages of interest:
Firmware Binaries
See archive.traverse.com.au
Source code
Just about all Ten64 firmware is under the traversetech/ls1088firmware group on gitlab.com
The firmware-builder project is the one that bundles the major components (ATF, U-Boot etc.) together
IRC
Some of us hang out in the #ten64 channel on the OFTC IRC network.
Keep in mind due to the wide timezone distribution of us and our userbase, there may not always be someone active in there.