Phone suddenly unusable after full discharge, no UI but a power menu

My OnePlus 7 Pro suddenly became unusable after fully discharging it. I never had root nor did I ever unlocked my bootloader on it. I just happened to completely drain the battery down to 0% until it powered itself off, and after turning it back on once it was charging resulted into pretty much all apps (with very few exceptions) not opening with the error:

<app_name> failed to start several times. Restore it by clearing history?

After several reboots, even the lockscreen UI stopped working, flickering the wallpaper image for a few moments every once in a while and going back to pitch black. Pressing volume keys does nothing, however holding the power key brings up a menu with: lockdown, power off, restart, and "Bug report - 12 (SKQ1.211113.001)". The phone also shortly vibrates every two seconds.

While the phone is plugged into PC via USB and powered on, it shows up as "SM8150-MTP _SN:<random_string>" with a caption "Driver is unavailable" in the Windows devices list. It also connects to my Wi-Fi router.

Any ideas what it is, why is that, and what to do?