I came across an investing find: a USB C to 4 × TTL UART adapter. This is essentially a USB hub with 4 USB–UART adapters. Plug it into your computer, and 4 com ports will be available.
So what would you use this for? Suppose you're working on several microcontrollers in some kind of network. Instead of a USB hub, a mess of USB cables and USB-UART adapters, all of this is combined in one small board.
In my case, I have a variety of small panel-mount devices, including buck and buck/boost power supplies, a temperature meter (more of a thermostat with relay output) , an electronic load, a PWM motor driver and others. Many of these modules have UART interfaces for control and data logging. A collection of ~$10 modules and you have the start of an automated test system. How about a test system where you can automate battery charging with controllabe voltage/current with temperature monitoring with over-temperature disconnect, then automatic discharging at controllable rates?
A couple examples of modules I have, all in the same panel-mount enclosure. The "Frequency Meter" is actually a PWM signal generator despite the label.