All
So I believe I have discovered the issue. I used my other FTDI USB to serial adapter which just has a simple pin header on it. I wired it up using a spare diode and 10k resistor for a pull up for single wire comm and it consistently works even in windows with the latest version of CHIRP.
I took apart the ttl2usb dot com device and took a look at what I had been sold. It looks as though best I can tell is that I'm only getting 2.8V on what I expect to be a 3.3.V pull up on both the TX and RX while in idle. So something is definitely amiss with the ttl2usb dot com supposed Yaesu interface. Must have been sheer luck getting it to work at all on my linux machine.
Does anyone have a link to a canonical (way it should actually be done) to turn serial into a one wire comm for the vx6-r a specific pull up resistor/diode combination?
It's pretty annoying that this ttl2usb dot com device I bought ages ago either broke with age (doubtful) was wrong the whole time and I just got lucky the levels worked every once in a great while.
-Nic