This worked after I tried a lot of options that did not work. Everyone was talking about some files named “deuxvis-1.05-digispark-d5-progbutton.hex” or “micronucleus-1.06-jumper-v2” or similar, but in the end, what worked was (assuming drivers for Digispark are already installed i.e. you are able to install software on digispark the normal way).
Drag main.hex to the micronucleus.exe. I have both saved in Arduino\micronucleus-1.11\commandline\builds\Windows\ . The other files, if I understand correctly, restore the default bootloader (at least one of the other files does that).
After the micronucleus window closes, wait until you hear the disconnect sound from windows! (About 5 seconds).
Then, when you want to upload, connect P0 to GND and plug in after it starts to upload (the same 5s window). If P0 is not LOW, then the program starts immediatley.