This is an implementation of a much requested feature (three whole issues begged for it since 2021: one, two, three) that allows to process a folder of photos automatically. Let this hackish workaround exist until folks from DeOldify incorporate this feature into DeOldify itself.
This script should work well on Windows. Other OSes will require some tweaks to the script such as changes in the class names and the like.
To make use of this script you need to install AutoIt from this page (select the AutoIt Full Installation software). Then build your desired version of DeOldify into the .exe file. Place both the bulk-deoldify.au3 script and the built exe file to the folder where your black and white photos are located and double-click the script. Also, to ensure proper working conditions for the script close all windows before lauching the script and don't touch your mouse thereafter. In case the script stopped unexpectedly just kill it and relaunch - it will resume the process.
Run the following commands in the console:
git clone https://https://github.com/polomoshnov/DeOldify.NET.git
cd DeOldify.NET
wget https://github.com/ColorfulSoft/DeOldify.NET/releases/download/Weights/Artistic.model -O Implementation/src/Resources/Artistic.model
Then go to DeOldify.NET\Implementation and double-click Compile.artistic.simd.float.bat.
Finally, go to DeOldify.NET\Implementation\Release and grab the exe file.
If you don't need to build DeOldify by yourself you can just download the exe file at the following address: https://github.com/polomoshnov/bulk-deoldify-with-autoit/releases/download/v1.0.0/DeOldify.NET.artistic.windows.simd.w32.exe