solution I have used:
- Put all your files in a google drive folder
- create a Google sheet with 2 columns: Column A has your file names, Column B has the formula =rand() next to all file names in column A
- Google Apps Script that refreshes the sheet every day at midnight (I assume you do this daily, but it can be any interval you need)
- Make module (google sheet ‘search rows’) that pulls the value in column A based on a descending (or ascending) order in column B. This is the part that randomizes the selection
- Make module (google drive ‘search files/folders’) that searches the folder from #1 for the file name from #4
- Make module (google drive ‘download file’) that downloads the file output from #5