How to access phone without display and touchscreen?

tl;dr: I want retrieve data from a phone that has a blank screen and is not responding to touch inputs.

Story:

The screen blanked suddenly and never came back on. I would like to retrieve the data from this phone. It is otherwise working, able to boot, receives notifications (sound, vibration and light) of incoming messages, rings when there is incoming calls. Pressing and holding to the power button for about 13 seconds restarts the phone. Screen lights up while booting but nothing appears on the display.

Troubleshooting done:

Tested with another motherboard and found out digitizer and LCD are actually working. So, replacing the screen would not help.

Futile attempts made:

1. Using a mouse via OTG, successfully unlocked the pattern lock blind after numerous (hundreds of) attempts, thereafter, I was able to unlock using fingerprint. Will require to blind unlock again after reboot. Tried to access internal storage by connecting to a PC via USB but to no avail because it connects as “charge only” by default and I have no way to change it to MTP because the USB is in use and I could not connect a mouse or keyboard via OTG at the same time.
2. Attempted to map out keystrokes solely using keyboard via OTG with a working phone (even though the keystrokes are probably different) to enable developer options, USB debugging, etc.. However, it was discovered that once connected to PC, the phone will require an input to allow or deny USB debugging, which I have no way to input.

Phone model: Redmi 3S Prime

Any help or suggestions will be greatly appreciated.

Another question: I know that connecting the OTG to an USB hub will enable the phone to host multiple devices (keyboard, mouse, flash drive, etc.) simultaneously. Does the phone allow connection to PC and input devices concurrently? If so, do recommend products that are capable of enabling such tasks.