I understand it doesn't have to be a NAS but it would be much better in my opinion. RAID enclosure over USB is...well, not the most reliable solution. I would look into some Synology options. As has quite nice DSM and it can combine drives of different size in the SHR RAID: https://kb.synology.com/en-af/DSM/tutorial/What_is_Synology_Hybrid_RAID_SHR
Data Hoarder
We are digital librarians. Among us are represented the various reasons to keep data -- legal requirements, competitive requirements, uncertainty of permanence of cloud services, distaste for transmitting your data externally (e.g. government or corporate espionage), cultural and familial archivists, internet collapse preppers, and people who do it themselves so they're sure it's done right. Everyone has their reasons for curating the data they have decided to keep (either forever or For A Damn Long Time (tm) ). Along the way we have sought out like-minded individuals to exchange strategies, war stories, and cautionary tales of failures.
The cheapest solution would likely be a Mediasonic Probox or some other USB drive, throw some 20 to 22 TB drives in that, and call it done. The ideal solution would be to have a four bay NAS with RAID 5 or (even better) RAID 10, so you can keep snapshots, the NAS can optionally do backups, etc.
What about this QNAP for a direct-attached storage solution (it also works standalone without a NAS, which is how I’d be using it): https://www.bhphotovideo.com/c/product/1454549-REG/qnap_tr_004_us_qnap_tr_004_4_bay_usb.html
with these drives: https://www.newegg.com/seagate-exos-x20-st20000nm007d-20tb/p/22-185-011?Item=22-185-011&cm_sp=product-_-from-price-options (the only good NAS HDD BlackFriday deal I've seen so far).
Overkill on storage space for sure, but at least somewhat future-proof..? What do you think?