Anyone who knows me even a little bit understands my archivist tendencies. I love storage, specifically hard disk storage, and the challenge of manipulating data efficiently. A while back, I created a list of the most intriguing data utilities with a variety of features for backup, sync, archival, encryption, and others.
Note these aren’t cloud services specifically, but may have the functionality to interact with cloud providers like google drive or s3.
Many of these are well known in the linux and self-hosted world. You should be able to easily find each by googling for it and looking for a main site or github repository. Some of the highlights from the list which I have either used myself with great success and/or heard good things about include Restic, Nextcloud, Rclone, and Duplicity. Things like git-annex are extremely interesting but can be complex to get working effectively.
Ensure you understand exactly what you need out of a storage utility before picking something that might be way more (or less) than what you want. Also, always interact with the tool with some test data first to ensure data integrity after syncing, backup, or other action.