P: Allow Catalog to be stored on a networked drive.

"The 4 bay drive dock is connected via network cable"

A USB 3.1 connection, if your computer supports it, would be more than fast enough for a fast SSD and twice as fast as a 5 Gbps Ethernet network cable (a USB 3.0 connection would be about as fast).

Barring that, you could put the catalog on an internal or external drive and everything else, including previews, on network drives.  Many people report success in locating the previews subfolder on a different drive from the catalog folder using symbolic links and junctions: 
https://www.lightroomqueen.com/community/threads/how-to-move-previews-from-ssd-to-hdd.24282/

The .lrcat catalog file itself takes relatively little space -- about 1 GB for 32K photos -- so it is more feasible to keep it on an internal drive.  

The received wisdom is that the catalog file should be on a very fast drive for the best performance. But in my own testing, I've observed that the .lrcat file, being relatively small, gets cached in memory by the operating system, so the speed of its disk is relatively unimportant (as long as you have enough memory -- your system has only 12 GB, so Windows may not cache a 5 GB .lrcat file in its entirety).

Previews are much smaller than their corresponding masters, so even slower disks have more than enough bandwidth to transfer previews faster than you can view them.  What matters perhaps more is the latency (how fast they can access a new file), and here direct-attached drives almost always outperform network-attached drives, which usually has much higher latency.

Lightroom Classic version: 8.1 [ 1200465 ]
License: Creative Cloud
Language setting: en
Operating system: Windows 10 - Home Premium Edition
Version: 10.0.17134
Application architecture: x64
System architecture: x64
Logical processor count: 4
Processor speed: 3.4 GHz
Built-in memory: 12235.6 MB

The 4 bay drive dock is connected via network cable to the back of my desktop system that is the only computer here I'm using.  The other computers here in my house don't get my stuff.  I don't want to share the catalog.  I store the picture files just fine on another physical HD in the drive dock using a different drive letter.  I use M: for the memory/SSD drive, and P: for the physical HD.

This is a different topic because I'm not interested in sharing the catalog on more than one computer and I don't want to use an external drive squeezing through a USB port.  My pictures work just fine on the external HD through the same networked dock because I seldom do anything to the source files themselves.  I would love to be able to keep my previews on the SSD because it would be the rough equivalent of keeping them in memory.  It would let me speed through looking at large numbers of my #150K+ photo collection and weeding out stuff that I only need backups of and not actually hanging around in my catalog and slowing things down.

How is the new drive connected to your computer -- via network (NAS) or a cable (USB, SATA, Thunderbolt)?

As others have pointed out, you can't store LR catalogs on network drives -- that's a fundamental limitation of LR's implementation.

But if the drive is local (internal or attached externally by a cable), then you should absolutely be able to store a catalog on it, regardless of whether it's internal or external.  The operating system (Mac / Windows) may be reporting to LR that the drive is read-only or removable (like a USB stick) -- that happens infrequently for various reasons.

If you copy here the first ten lines of Help > System Info, we can start troubleshooting.

"Lightroom Catalogs can not be opened on network volumes, removable storage, or read only volumes."  Why not?

After buying my new SSD to pop into my drive dock, and copying my catalog/previews files from Lightroom over to it to improve the system performance, I'm advised "NOPE!"  Adobe needs to fix it.  If I am going to continue to lease this software for $120/year then they should make my system handle my 150,000 + images much faster.

I have Lightroom installed on my mac mini. Now I want to use it as well on my Win10 Laptop. Without having the catalog on my QNAP NAS, this is not possible.
Anyway, if QNAP continues developing that quick and Adobe provides no solutions for local installation anymore, I won't use Lightroom anymore.
Cloud service does not provide GigaBit network traffic for affordable prices!

How does symbolic link work with mac?

One thing I don't understand is why LR cannot open a catalog stored on a network share. I use to work locally for the current set of picture, then move all the pictured and related catalog files to a NAS. But if I have to open the catalog again, I have to move it back to the local storage. I understand working from the NAS would be slower, but it would be ok if I have to work on a single picture.

Hi Robert,

The behavior that you describe is expected.

Camera Monochrome profiles (such as those found in the Camera Matching set for your Fuji camera) were designed in such a way that when applied, all color is removed. The B&W Mixer sliders are disabled in this instance because without color data, the mixer has nothing to work with. This is why the “Monochrome profile applied” messaging appears in the UI.

Adobe Monochrome on the other hand, leaves those colors intact by using a different method of conversion under the hood. It was intentionally designed this way so that the B&W Mixer would remain enabled (as were the profiles found in the shipping B&W set). 

If access to the B&W mixer is important to your workflow, you might give the profiles in the default B&W set a try, as they allow far more control (profile amount slider, access to the B&W mixer) than do the legacy Camera Matching profiles. 

Anybody else experiencing the same behavior?

This is similar to how people use Dropbox and similar services to sync catalogs between computers. With any of these approaches, you must be careful to have LR open only one copy of the catalog at a time, or else corruption could occur.