Can't flash ESP 32 Wroom
I did fix the problem now. 

My mac has USB-C and I was using a single USB-C to USB Dongle. And the serial port never showed up on my mac:

crw-rw-rw-  1 root  wheel   18,   5 Mar  8 10:53 /dev/cu.Bluetooth-Incoming-Port
crw-rw-rw-  1 root  wheel   18,   7 Mar  8 10:53 /dev/cu.Heinz-WirelessiAP
crw-rw-rw-  1 root  wheel   18,   3 Mar  8 10:53 /dev/cu.MALS
crw-rw-rw-  1 root  wheel   18,   1 Mar  8 11:02 /dev/cu.SOC


As soon as I used the Satechi USB Dock the Silicon Labs USB to UART port showed up in the list:

[...]
crw-rw-rw-  1 root  wheel   18,  13 Mar  8 11:04 /dev/cu.SLAB_USBtoUART


I can now communicate with the ESP32:

esptool.py --port /dev/cu.SLAB_USBtoUART read_mac

esptool.py v2.6
Serial port /dev/cu.SLAB_USBtoUART
Connecting........___
Detecting chip type... ESP32
Chip is ESP32D0WDQ6 (revision 1)
Features: WiFi, BT, Dual Core, 240MHz, VRef calibration in efuse, Coding Scheme None
MAC: XXXXXXXXX
Uploading stub...
Running stub...
Stub running...
MAC: XXXXXXX
Hard resetting via RTS pin...


Please note that if you'll need the Drivers for the USB to Serial Chip from Silabs. 

If you do not see the device showing up you'll need to load the kernel extension:

sudo kextload /Library/Extensions/SiLabsUSBDriver.kext/


After this you might to confirm the extension in the Privacy section of the mac settings. See this forum post for reference.