I've got a QNAP TS-451 and it works, but I don't find that the added features are really worth anything. I basically use it as a dumb storage server (NFS, SMB, and iSCSI) and for that it works really well. The only bit of smarts I use is the Hybrid Backup Sync utility to back up important folders to external drives and, when I get around to setting it up, some kind of off-site backup.
I've just found too many odd limitations with the device to use it for much more than that. For example, you can set up VLANs and you can bind services to specific physical network interfaces, but you can't bind a service to a VLAN interface. This is what made me give up on the added features.
Also, be aware that some added features have moved to a subscription model[0]. And, if you expose your QNAP to the internet, there's a risk of getting malware[1]. On the plus side, this has made them open up a tiny bit[2][3].
I've just found too many odd limitations with the device to use it for much more than that. For example, you can set up VLANs and you can bind services to specific physical network interfaces, but you can't bind a service to a VLAN interface. This is what made me give up on the added features.
Also, be aware that some added features have moved to a subscription model[0]. And, if you expose your QNAP to the internet, there's a risk of getting malware[1]. On the plus side, this has made them open up a tiny bit[2][3].
[0] https://www.reddit.com/r/qnap/comments/hmsw6a/beware_of_prem...
[1] https://www.theregister.com/2020/07/27/qnap_attack_warning/
[2] https://www.reddit.com/r/qnap/comments/fd0g71/psa_im_having_...
[3] https://www.reddit.com/r/qnap/comments/fgmeu3/psa_qsnatch_up...