Mount a remote file system via SMB or NFS and it'll work like any folder on your PC - but you need a network connection to access it. If you need offline mode, maybe create a folder /offline and replicate it to your hard drive with a bidirectional synchronization tool like unison or syncthing. As for providers, personally I use Hetzner Sotrage Box because the price and service looks good enough to me that I didn't bother to look for alternatives.
KDE Discover is a GUI application for adding/removing packages from different sources
When I was in middle school, the techy kid walked up to me with a piece of metal in his hand and said, hey, did you know you can take out this part of a lighter and use it as a taser? I thought he was cool and immediately took a liking to him. Turns out we took the same train to school, and soon enough we'd share our train rides. Soon after, he started staying over at my place. One day he was chilling on my bed and installed something on his laptop called "Mandriva Linux". This is the day I met GNU/Linux <3