You could ask the question for video gaming. Can a used computer do the job? Yes, but you may not be able to play cutting edge / demanding games if your computer lacks the appropriate hardware. It really depends what kind of things you want to do, for choosing hardware that's powerful enough.
Jellyfin? You need to consider if you need transcoding. Transcode or not makes quite a difference on the hardware needs.
You could ask the question for video gaming. Can a used computer do the job? Yes, but you may not be able to play cutting edge / demanding games if your computer lacks the appropriate hardware. It really depends what kind of things you want to do, for choosing hardware that's powerful enough.
Jellyfin? You need to consider if you need transcoding. Transcode or not makes quite a difference on the hardware needs.