I solved my desk space problem by using a much smaller computer: the $10 Raspberry Pi Zero W. (The $5 Raspberry Pi Zero is the same, except that it does not have WiFi and Bluetooth.) The Raspberry Pi is primarily an educational computer, but has also found a huge number of practical uses. Raspberry Pi runs Raspberry OS, which is a customised version of Debian Linux, as is Ubuntu. The Raspberry Pi Zero is the smallest and cheapest member of the Raspberry Pi family.
I initially set up the Zero as a desktop computer using an iPad charger, USB hub, monitor, keyboard and mouse. The first step was to install the Raspberry Pi Imager on my desktop computer and burn the image of Raspberry OS onto a micro SD card:
I then inserted the micro-SD card into the Zero, and was able to boot the Zero and use it as a desktop computer. It was not fast, but it appeared to be fast enough for my purpose.
I connected the Zero to the Novag Citrine using a vacant slot in the USB hub and the USB serial converter that I used previously. I opened the Raspberry Pi terminal and typed:
dmesg | grep tty
The list included "pl2303 converter now attached to ttyUSB0", which is the entry for my USB-to-Serial converter. I typed:
I got warnings, but the CuteCom window opened nonetheless. I selected dev/tty/USB0 from the Device pull down.
Click Settings, and select 57600 Baud, keeping 8 Data bits and 1 Stop bit. Click Open. Select CR/LF.
I typed p in the Input field followed by <CR>, and received the board position in response.
I was also able to access the Zero from my desktop computer using SSH:
Menu > Preferences > Raspberry Pi Configuration
Click on Interfaces, set SSH to Enabled and click OK. Open a terminal and type:
The IP address is returned. I will call it <ip_address>. Open a terminal on another Linux computer and type:
Enter yes and press RETURN. Type the Raspberry Pi password. You then have remote access to a terminal on the Raspberry Pi. Typing exit to closes the SSH session. It is also possible to transfer files between the two computers over WiFi using SCP, as described in the MagPi article linked above.