Almost al the guides i found of recent time said update firmware.
In most devices, updating FW is a good practice. The DJI drones are an exception. I mean, every material from DJI will urge you to update. But after so many years, the users know better.
I tried 3 different usb c cables both primary charge and primary data.
It's up to you to decide whether that was enough of a verification. If a cable is confirmed to work for data transfer somewhere else, there's little chance it wouldn't work for the drone.
You could try an older mobile device, if you have one using micro-usb-b.
Sometimes there are issues on mobile with permission to use the usb device - did you get a monit about which app to use after plugging the USB?
Also, while I never did that personally, it's probably a good idea to check if the RC "talks" to the phone - there are apps for listing connected USB devices. I found this one:
Show USB device details like VID, PID, Class, Interfaces, Endpoint types.
play.google.com
If the device isn't listed there, and you checked enough USB cables - the possibility of interface board in the RC not booting becomes the most probable option.
My guide for fixing firmware in the interface board is here:
Technical details and howtos about DJI drones. Contribute to quaddama9e/dji-technical-stuff development by creating an account on GitHub.
github.com
You will find other guides for fixing the DaVinci chip firmware, including video ones. Most are focused on fixing the same chip within gimbal (your model doesn't have it), but the procedure is very similar. Also most of such guides are making more assumptions and providing less explanations - up to you to decide which one you want to follow.
And yes, at this point you will need soldering station, some skill (better try soldering some junk first, or you will damage the pads), and the USB-to-TTL converter.
Or, another GL300a/b/c RC.
EDIT:
for the log you provided - we can't get much information from your transcription. Here is how you should expect the log to look like:
Here is the hidden log file:
[00230711]Version checking[2]...
[00243330][03 05][00] device not detected.
[00255956][03 06][00] device not detected.
[00256066][04 00][00] v1.48.0.0 -> v1.44.0.0
[00268673][11 00][00] device not detected.
[00281286][12 00][00] device not detected.
[00293894][12 01][00] device not detected.
[00306507][12 02][00] device not detected.
[00319119][12 03][00] device not detected.
[00341742][15 00][00] device not detected.
[00354359][17 00][00] device not detected.
[00366967][17 01][00] device not detected.
[00379579][19 00][00] device not detected.
[00379687][01 00][00] v1.25.5432 -> v1.23.4920 need upgrade
[00379796][01 01][05] v1.23.4920 -> v1.23.4920
[00392404][09...