The more common versions are a diode and capacitor or the transformer directly for the gate signal.
I've looked into the idea of using gate drive transformers a bit, it seems to me that they are used at higher frequencies. I'm planning on switching with 16kHz and 18V, which would make my V*t product 1125uVs and with a quick search of Wurth electronic gate drive transformers i noticed most of them are in the range ~50-100uVs. Unless my logic is wrong, that would make the gate transformers saturate way too soon.
As for the bootstrap method, it's my understanding that this method is used for lower voltages and I'm planning to upscale this prototype to 600V at a later stage.
One other reason why I assumed the flyback configuration would be more common is that the Tesla model 3 inverter uses it as a main power supply option for it's gate drivers.