How to recover from recovery boot loop in Galaxy A20? Everything was fine on my rooted device with magisk, until I flashed a custom recovery (TWRP) on RECOVERY partition.
That didn't work, resulting in a message "recovery error validating footer vbmeta" during boot into "download mode".

Perhaps the device was still ok after that.
However, trying to fix the message and put TWRP to work, I flashed a vbmeta.img on VBMETA partition.
This resulted in the current boot loop, I suppose because of some checksum regarding vbmeta and the (stock) root partition.

Is there any hope for this device? 

I am still waiting for the battery to drain, but so far all the attempts with using the buttons/USB failed to be able to communicate with the device in any way.
I does anything other than just rebooting.
Following @alecxs advice, I managed to exit loop and enter download/odin mode:

1) Just drain the battery until it turns off.

2) Hold vol+ and vol- while connecting usb cable.

3) Press vol+ to enter download/odin mode.

ps. The fix of the system is subject of another question.