You can install replicant 6 without PC if you have TWRP
I'm using Samsung Galaxy Note 2
I tried yesterday flash the Replicant Recovery.img with TWRP's install image function and it working like charm.
I just follow these steps.
Download Replicant Recovery.img and Replicant Rom.zip
Then I go to TWRP recovery.
Install --> Install image (Bottom Right) --> Select "Replicant Recovery.img" --> Select "Recovery" -->Swipe and Flash now.
After flash succeeded without any error I go to main menu and I used Reboot Recovery function inside of the Reboot section over on the Main Menu for test the Replicant Recovery.
Then it worked and I can see the Replicant Recovery.
After that I followed normal guide to install the Replicant Rom. And I installed Replicant Rom without any error.
My note2 (n7100) is now running Replicant OS. And Im writing that lines from My note2 (n7100) with Replicant OS.
I supposing it can work on the other devices which is has TWRP with install image function.
Sorry for my painful English.