While Apple has iCloud and M$ has OneDrive, both offering 5 free GB of storage, most Free backup services written for Linux are focusing on saving your data to your own hard drive lying next to your computer. That is troublesome and not the most reliable as in case of a house fire or a flood it will burn or drown along with the machine. Some offer an option to buy some storage from a third-party provider like Amazon, but that’s again non-open and troublesome.
Is a free&Free peer-supported service possible? Where, similar to torrent tech and PeerTube, you allocate some storage on your PC to someone’s backups, and can publish your data on the network in return, so that data would be distributed between computers and could be requested on demand?
I dont have any experience with any of these but you may find some options by searching for web3 or dapp storage solutions. Example best of list.
web3/dapps are an attempt at making fully decentralized web applications using blockchain and other decentralized technologies. Since storing large volumes of data on a blockchain isnt the best idea, projects like IPFS and others on the first link I shared emerged to fill the gap.