ProtonDrive is listing "open source" as one of it's main features. They provide links to source for Android and iOS apps. Are there any hurdles to build an open-source Linux client, that would work like classic "dropbox", just syncing files between ProtonDrive account and local computer?
Proton has a rather "curious" interaction with the word "open source".
Most of the time, they wait to release the source code of their products around the time a specific version is released, and perform active work on a hidden or private clone tree.
It's better than other companies, but isn't the type of open source you typically see with most FOSS projects.
As for ProtonDrive, I don't see the source code anywhere (other than Android/iOS version). Where are you seeing this? I'm assuming both offerings use Windows/macOS specific APIs (at least I hope), so you'd need to go through a large amount of engineering effort to get it working with Linux, and that's before even choosing how to implement it. FUSE driver? Nautilus extension? Electron web app?
I was looking into source code of Android app [1], as it is supposed to be current version of app on Google Play Store. Of course the local build failed, even after adding required properties file that readme did not mention.
Source for web app [2] is archived, maybe it was merged with mail webapp?
And I stumbled upon Celeste [3], but it has bug reports about not being able to connect to ProtonDrive.
You can connect 2X10TB to a PI, mini PC or similar at home and access your files over a variety of interfaces (SFTP, nextcloud, syncthing, etc) using a vpn such as Tailscale. Why does one need to pay for expensive storage?
For me it's reliability: I don't have to think about power or network outages, hardware failures etc., and after doing sysops at work I don't have to come home and do the same thing on my own stuff or servers. (the only thing I need to care about is backups)
It's similar reasons to why people choose to pay for e.g. AWS instead of buying physical servers and colocating them.
Because, while you or I might be able to do it, a lot of people don't want to do this. They'd rather have it work and not need to think about it. There's a lot to be said (and pay for) convenience.
Most of the time, they wait to release the source code of their products around the time a specific version is released, and perform active work on a hidden or private clone tree.
It's better than other companies, but isn't the type of open source you typically see with most FOSS projects.
As for ProtonDrive, I don't see the source code anywhere (other than Android/iOS version). Where are you seeing this? I'm assuming both offerings use Windows/macOS specific APIs (at least I hope), so you'd need to go through a large amount of engineering effort to get it working with Linux, and that's before even choosing how to implement it. FUSE driver? Nautilus extension? Electron web app?