Enabled USB bus without connecting input devices to USB

This might be user error, I apologise if so. I've been trying (quite successfully) to install Windows 98SE, the only minor weirdness is that I have to set "USB Support" to "Off" in order to connect the mouse and keyboard as PS/2 devices, so that input works and I can correctly configure the PCI Bus inside Windows.

Once configured, USB should work, but when you turn USB Support back on, PS/2 input devices disappear, which means it's impossible to complete the "Add New Hardware" wizard for the new PCI to USB Universal Host Controller.

Is it possible to enable the USB bus, without connecting the mouse and keyboard to it?

I thought that "Force PS/2 controller" in the QEMU settings might do this, but it does not.

**Configuration**
* UTM Version: 3.2.4 (58)
* OS Version: macOS 12.4
* Apple Silicon

[debug.log](https://github.com/utmapp/UTM/files/8994871/debug.log)
[config.plist.txt](https://github.com/utmapp/UTM/files/8994874/config.plist.txt)