No matter what serial-esque protocol you need to interface with, this USB to Multi-Protocol Serial adapter will be able to get this-connected-to-that. It supports RS232 serial, TTL UART serial, RS485 and RS422. All with quick-connecting screw terminals so you don't need to do any soldering or use special cables.

Just plug directly into a computer's USB A port and use a Phillips screwdriver to open the terminal and insert a solid or stranded-core wire. The USB A is even the flippable kind so you will always be able to have the labels and LEDs facing you.

Inside is a FTDI FT231 USB to serial converter - this chip uses 5V logic and provides the UART serial signals that are converted into the different formats. Supported signal rates are 300 baud to 3 Mbaud. FTDI drivers are built into just about every OS these days - but if you need to install, there's free VCP drivers.

For the RS-232 signal side, theres a UM213 signal level converter with +-8V logic level I/O. All eight (5/3) RS-232 signals are exposed. The RS-232 converter can handle up to 250kbps.
For the UART signal side, it is connected directly to the FT231. Logic level is 5V, and only RX/TX and 5V/3V/GND are exposed.
For RS-485/RS-422 signal side, the UART RX/TX lines are connected to MAX485 chips.
As a bonus, you also get 5V and 3V (with matching Ground) power supplies to power small projects - the 5V is from the USB so its technically 500mA but you can probably draw 1A, 3.3V is from the FT231X and is 50mA output.
Red 'Power good' LED, Green 'Data transmission' LED

Please note: there's only one USB-serial chip inside, so you can only use one protocol at a time!