com0com: not working with secureboot
My first idea was: let's try com0com, since this is the way to go on other platforms. Unluckily, I was not successful to get the created connection pairs in the right device group in the device manager. They were always in "com0com - serial port emulators" not in "Connectors (COM & LPT)". Additionally, the connection (see properties-> events) was configured, but not started. Searching the problem code 0x34 (in dec: 52) on the microsoft page leads to "Windows cannot verify the digital signature for the drivers required for this device. (Code 52)”
This problem did not disappear with the signed version of com0com from source forge. I also did not succeed in finding a different signed version.
A workaround is to disable secureboot on startup, which is not an option in my case.
free-virtual-serial-ports: kind of working
One feasible solution is the freemium tool "free-virtual-serial-ports". It allows to set up a connector pair COM1 - COM2. The free version has also some major limitations like: only one pair possible, no change of the COM name allowed, etc.
The tool can be downloaded via freevirtualserialports.com/features
other freeware / open source tools: ?
I would be glad to see some. Up to now I have not found any, working with the secureboot restrictions of WIN10..