Self hosted file sharing
If you’re trying to be less reliant on cloud services and such to manage your digital stuff, one of the problems you may run into is going to be accessing the same files across multiple devices without help from the cloud. It is pretty important to make the distinction between two different purposes for file sharing. Firstly, you may be using file sharing to get more storage. In this case, your large amount of files will be stored on a single computer and then you will want to be able to access them at any time. This is obviously good for files of large size that wouldn’t fit on the computer you directly use, such as movies or backups. You will probably need a dedicated machine to do this that’ll sit on your network at all times. I would suggest installing an operating system like OpenMediaVault so you can manage it entirely remotely. It’s also probably going to be significantly easier than going with a base Debian install or something.
The other purpose of file sharing is redundancy. Basically if your computer gets destroyed, you want to have your important files stored safely elsewhere. This is different because you want the files to be stored on many computers. My favorite, easy to use software to do exactly this is called Syncthing, which you can use on basically anything, and it works by making sure certain folders are automatically duplicated to other computers.
Why would you go through all of this? Well, if you are using services for option 1, every data storage provider will begin to cost a lot (and charge per month) the more GBs that you use. You can save probably hundreds of dollars a year by making a server of your own. The argument for option 2 is not as strong, but maybe you don’t trust big companies to take good care of your files, or you want to add more points of failure to your master database.