How to setup a reverse USB tethering connection (multiplatform)?
For documentation purposes here is an expanded version of the comments.

Option 1: SimpleRT does work and the device gets an IP on the local network which is a plus. On the downside, it supports a single android device and doesn't support hot-plugging at the moment, however, the software is free and open-source (another plus)

Option 2: Reverse Tethering NoRoot. 
I've tried the free app and it's a great app: minimal easy to understand UI, the server app on desktop is brilliant in it's simplicity. It supports multiple clients and hot-plugging (great pluses to have). At the moment it doesn't look like the android device gets an IP on the local network which would be great feature.

In conclusion: if you simply need to connect multiple android devices to the internet via USB and don't mind the lack of a LAN IP for the devices, Reverse Tethering NoRoot is the easiest option.