Since Portmaster is open-source, I expected that I can modify and compile the software by myself. Maybe I will hack around when I have time.
Is compiling locally not possible without the signing cert?
Most repos have a "./pack" script that correctly builds all assets. You can then place them as "v0.0.0" (as _v0-0-0) in the updates directory. If you put Portmaster into dev mode (--devmode) it will load the v0.0.0 versions first. You might want to also disable automatic updates - or ignore the automatically downloaded versions.
Compiling for Windows without a cert works, but the OS will refuse to load the driver. You'd need to switch to a special Windows developer mode and sign it with a local certificate.
As I said, this is an area where we need to improve.
The thing is that Portmaster consists of a lot of components[0]. I don't think we'll get around creating a docker image that does all the steps automatically - as far as possible. For Windows this will be infeasible for most, as you need a EV Code Signing Cert (300$+) for signing the kernel extension.
Can you elaborate on your use case?
[0] https://docs.safing.io/portmaster/architecture/update-system...