Juraj:
yes 2.3.0you have a 'pro' version without usb and attached reset circuit, so the flashing tool (not ide) can't set the board into flashing mode
to set the board into flashing mode, io 0 must be low at power-up or reset
I have this model here: https://wiki.wemos.cc/products:d1:d1_mini_pro
and I am using the built-in USB connector to flash it (which works most of the time - unless the device does not like the uploaded .bin and goes into "crash"-mode - which is the scenario that I am refering to in this post)
Add-on: I meanwhile realized that it might just be the LCD display (or it's respective I2C controller) that ends up in some crashed state: I found that I could upload code like the "LED blink" example that would actually work - even when I could not get my LCD based example code to display anything (from which I had earlier had the impression that the complete device might be crashed). It seems that the LCD's "crashed" state can last for a while and it even persists when the power supply is disconnected for some seconds..
So the root cause here might actually be I2C related - or whatever puts the LCD in that "crashed" state.