The options offered in Retrovol are dependent on the driver being used and the Linux kernel being used.
The Linux kernel provides the driver.
Basically, change the Linux kernel, used in Tahrpup, to a newer kernel, and the option should be offered.
This worked for me to get loopback option in retrovol in Tahrpup64 6.0.6.
Also, made my sound card work better.
Note:
A small chance this could make something else not work, but it would usually happen on really, really old hardware.
Here is how to change the kernel:
In a console enter:
In the change_kernels window click on kernels button.
That will open the browser to the repository for kernels used in Puppies.
Select one of the kernels being used by Xenialpup.
Make sure to get the correct 32bit or 64bit that matches the Tahrpup bit version you are using.
Download the .tar.bz2 kernel package to some easy to find location.
Now you have to unpack the .tar.bz2 kernel package.
In Rox file manager navigate to the download location.
Left click on the .tar.bz2 kernel package.
XArchive should open showing the contents of package.
Click on select all.
Click on extract.
Click on OK.
Now should have two new files in the location of the .tar.bz2 package.
a vmlinuz file.
kernel-modules.sfs-XXXXX (or similar) or could be zdrv sfs.
Now back at the change_kernels window.
Enter these files in the entry boxes.
vmlinuz file for the first entry box.
kernel-modules.sfs-XXXXX or zdrv sfs for 2nd box.
Hit OK.
The program should change the kernel with no errors.
If all went correctly.
Reboot now using the new kernel.
Note:
Anything that is compiled for a specific kernel will have to be recompiled.
Example:
A manufacturers graphics driver is kernel specific.