I don’t nas, but I suggest a combination of offline drives, cloud services or remote hosts, and just ignoring data that is easy to recreate like builds and software installs.
The key is to keep the data organized in such a way that you know which parts deserve which strategy.
I really hope it would be a working one, not like xfs where your files may just disappear with no trace (never on Irix, never on any other fs) or like btrfs which may just suddenly go read only and be dead on reboot with no fsck and all data unreachable.
How hard is it to get the basics right? Doesn’t matter how much rice there is if it keeps blowing up.
You can only compress data to some extent. You could see if any of the files are encoded in an older or less efficient codec than what you have. Transcoding does introduce some distortion, but usually not too bad for utility use like learning material.
The other option is to get rid of some data. Delete some of the files. Use a (non-recompressing) editor to clip out parts you don’t need. Transcode with lower resolution and/or bitrate/complexity.
It all depends on what you have and what you’re able and willing to do with it. There is no universal silver bullet to get you more storage space. Other than actually getting more storage space.
That is a good mindset and you should hold on to it. Of course a gui can install a keylogger for you just as easily if not more so.
Trusted install sources, usually called repositories, are the way. Chances of malware exist, but they would require some spectacular shenanigans or conspiracies to set up.
Though this reminds me that I remember getting my first skis. But don’t remember learning to ski in particular. Skis and snow has just always been there. I think I know where they are still today.