You can try the mirrored card to see whether or not it was updated. Nothing to lose if it doesn’t work. Otherwise, you’ll have to go to your backup.
Assuming you get it working and want to stick with OH3 for now, the link given by @lfs_alp5 has the commands needed to avoid updating to OH4.
There’s generally a new release (major or minor) annually. OH4 was released over a year ago, and the 4.1 version came out in December. Just something to keep in mind in the future.
I recently wrote this tutorial to help users regularly keep tabs on releases by email. We know that a lot of people don’t visit the community regularly, which makes it difficult to stay up to date.