I don't know about the 5150 in particular, but most of these USB to serial adapters will not work with older computers since they are expecting different voltage levels.
Unfortunately, many adapters advertise being RS-232 but the specifications go on to say they are TTL. (I'm not sure that's accurate either, but it is the vendor's shorthand for 0 V and 5 V levels.) Some won't say anything at all, which leaves compliance an open question.
Of course, this all depends on sane current limiting behavior from the 12V side. I'm sure there's at least one line driver out there that does a good "gnome swapping terminals on a car battery really fast" impression.
FTDI were good, but they went apeshit with the drivers bricking non-genuine devices, and I don't wish to support them if at all possible.
Prolific have always been troublesome, and their proprietary drivers refuse clones these days (which broke my chinese usb-rs232 dongle).
ch340 is very popular these days, but I've found they have little tolerance for slightly-off or jittery clocks.