It may be possible to configure it via Mainport/FlexiPort set as telemetry, but you need to configure that from current telemetry, which is USB unless maybe you currently have an OSD running... so chicken and egg. At least I don't think there is any automatic switch over to serial when USB is disconnected, but it doesn't hurt to try.
If you can get the USB to work correctly by bending something just one time, you could set telemetry to serial (USB off and e.g. Flexi=Telemetry?) and try an FTDI.
Other options might include removing USB connector and replacing it ... or cutting up a USB cable and carefully soldering the wires in the correct place where the USB connector used to be. I successfully used Kapton tape and hot air reflow to replace one once.
Although still very tiny, the chip that has the settings actually has the largest pins and could be replaced with one that has serial port set to telemetry, if you have another CC3D to set this up and test it and swap chips with. Again, probably Kapton tape and hot air reflow...
A standard CC3D is less than USD $10 and even fancy varieties are less than $15, so buying a new one makes the most sense unless you have equipment, time, skills, and desire (or a buddy with all these) to fix this one.
Edit: Hmmm, another option would be for a programmer friend to make a simple change to the firmware, a special version of firmware that does serial telemetry by default. Then you would install this firmware using FTDI and SBL method like you have to do if it has no bootloader or a different brand of bootloader.