avr_fred:
Based on the zero responses, there’s no bootloader or it’s corrupted.
hmm... doesn't bode well with the 2nd option.
avr_fred:
Why you where unable to install a bootloader is unknown. Connection issues would be the most obvious or something funky with your isp programmer. Eliminate the connections issues by installing the standard 6 pin isp connector in the open JP3 header and use an usbasp so you’re not messing with wire to wire connections every time you want to flash a board.
i will have to accept this is likely then, even though it has been proven successfully consistent with the 'Breaduino' and a ATtiny85.
avr_fred:
Repurposing an Uno is inconsistent at best due to the header connections which are made worse by using round wires rather than square pins. Just spend the $5 for an eBay usbasp and a 10 pin to 6 pin adapter board. That way, flashing a bootloader is done with a constant ten seconds of effort.
it's funny how all this started by trying to avoid having to buy a FTDI-breakout board...
(but, since i am now considering using a ProMini and getting a CP2102 USB-to-TTL adapter "for variety", i might as well add to that 'arsenal' and get the USBasp as well. if only so i can get a proper JP3 cable - can't seem to find that on eBay, using wrong search parameters ?? 
)
avr_fred:
If reflashing with a known good isp still fails, you’ve got a worst case scenario where either the fuses are wrong or the clock circuit isn’t oscillating, assuming there is no sign of processor activity. I’m unsure about that due to your earlier comments about a flashing led when the board is reset.
to be precise, it "pulses" while on, ie. getting power from the ISCP connection - and the LED goes off (out) when/while the reset button is pressed.
avr_fred:
The only way to fix wrong fuses when there is no clock is to provide an external clock or use a HV isp programmer.
well, that would certainly be another addition... (for the longer term)
anyway, i really appreciate all the time and effort you have taken to help me out on this - i think i'll shelve it for now until i get a USBasp programmer.