The results were a minefield. The first three links were clickbait portals promising the file but demanding credit card details for a "fast download speed." The next few were forum posts from 2018 with dead links, the files long since purged from MegaUpload or MediaFire.
If the above method doesn't work, you can use the SP Flash Tool to install the firmware update. Here's how: download file firmware update oppo f3 nougat free
Use the tool to check for the latest version and initiate the update. The results were a minefield