To directly answer your question, what you need to run Jellyfin is a computer with sufficient CPU, RAM, storage, and networking. Many NASs can fill this role as can Single Board Computers (e.g. Raspberry Pi).

The QNAP you listed here doesn't seem to have Jellyfin as an app, but it does have Plex. You can find this information on the manufacturer Website.

Hardware: https://www.qnap.com/en-us/product/ts-233

Apps: https://www.qnap.com/en-us/app_center/?os=qts&version=5.1.0~5.1.3&II=616

The type of hard drive required for this NAS is 'internal', what you have linked as your hdd is an external USB drive, it wouldn't work the way you are intending. You need an internal SATA drive. Two would be ideal.

Internal SATA NAS drive: https://www.amazon.com/Seagate-IronWolf-Internal-Hard-Drive/dp/B084ZV4DXB/qid=1700590050

With a 4-core ARM cpu and 2GB of non-expandable RAM, I'm not convinced it would be a good Jellyfin experience. It could at first, maybe for one user at a time; but if you wanted to expand its capabilities (eg. have two streams at the same time), you might not be able to. YMMV

Rather than this QNAP unit, you could go with something that has expandable RAM and the Jellyfin app available to the OS. As mentioned in other comments, Synology is a well-known brand with lots of community support.

Hardware: Synology DS224 https://www.amazon.com/dp/B0C6927XPX/ref=twister_B0CLWLQCT6

Internal SATA NAS drive: https://www.amazon.com/Seagate-IronWolf-Internal-Hard-Drive/dp/B084ZV4DXB/qid=1700590050

Which very nearly doubles the price of the QNAP, but has expandable RAM up to 6GB.

If you're willing to learn a little bit of Linux and CLI, for the price, you can't beat a Raspberry Pi 8GB. It already has more RAM than either of those units can provide, is cheaper to boot, and would use the External HDD you selected. There was a shortage for a couple years with COVID, but with the release of the RPi 5, these are becoming available.

https://www.pishop.us/product/raspberry-pi-4-model-b-8gb/

There are MANY guides on setting up Jellyfin on Raspberry Pi, like this one: https://pimylifeup.com/raspberry-pi-jellyfin/

Hello ! First question would be : why buy an external drive if you are buying a NAS in the first place ?

Just in case: there are 2 slots available in the NAS you sent, meaning you could buy 2 internal drives for its storage.

On the hosting part, Jellyfin might be able to run judging by the specifications of the NAS. However, you have to take into account if the NAS operating system can run it (maybe there is an app store for it like Synology) and also media transcoding might be limited (to easily stream around your house 4K content for exemple)

The only question I would say that decides what you get is, do you want files to be transcoded for clients or not.

If not, you can definitely use anything since you just stream directly. I use a Raspberry Pi 4, works perfectly with 3 users direct stream at home.

If you want to be able to supply transcoding you need to lookout for supported hardware, but I am the wrong person to talk about that, given I only use the Rpi4.