Seconding the suggestion of just getting an iMac 5K. As I mentioned below I just ended up getting a gently used 2017 iMac and work off of that -- $300 cheaper than LG Ultrafine 5K but with a Mac attached. (And less ugly, IMO.)

Just a clarification that "iMac (Retina 5K, 27-inch, Late 2014) and later iMac models can't be used as Target Display Mode displays" (support.apple.com).

It looks like you might be able to use a Luna Display dongle (~80 USD) to connect use a MacBook Pro with an iMac as an external display (or vice versa?). I've used Luna to turn an iPad into an external display (recently Sherlocked by Sidecar), but never tried Mac-to-Mac connection, so can't speak to its reliability.

Lunar is a free and open-source app that, amazingly, seems to let you control the actual brightness of external displays (I use it with an HP Z27 4K) using the keyboard brightness controls.

I've tried other apps that just place an adjustable-opacity black mask over the external display's content, but Lunar seems to actually be able to control the real brightness. It even lets you sync the external display with the built-in display, for automatic brightness adjustments!

Regarding O.P.'s question, I ended up doing the same thing as T.F. and just buying a low-spec 2017 iMac 5K on eBay for ~$1,000 instead of buying the LG Ultrafine 5K -- the iMac is cheaper, and comes with a computer attached. :)

(Nerd note: my iMac has a 1 TB Fusion Drive. My 2015 iMac 5K Fusion Drive was so slow I decided to boot off of an external, portable Samsung T5 SSD. But the 2017 Fusion is fast enough for designing in Figma and my front-end development work that I don't feel the need to do that. Of course YMMV.)

There's a new site called FindCollabs that might help. It might be more focused on devs than designers, though. (It's a creation of Jeff Myerson, the host of Software Engineering Daily.)

You'd think using a static site generator for a site with frequent updates would be a pain, but SSG-based sites (especially Hugo-based ones) can be quick and painless to build and deploy, daily or even more frequently.

With many (most?) webhosts you can transfer files over SSH, so setting up a script to deploy your site over SSH (using rsync, for example) can make deployment simple. Even better, as you suggest, is a continuous integration setup. As a designer, I thought this would be really complicated to set up, but it can be really easy with services like Netlify. Here are their instructions for setting up automatic building and deploying every time you commit changes to your remote Git repo.

@Matt Ronge It looks terrific. Since it can run over a wired USB connection, any chance of selling just the software at a lower price?

Nice site, but not responsive? I'd have thought a site like this, which I assume is aimed at the general public, should be mobile-friendly.

Update: Oh, it looks like it is somewhat responsive, but might be missing a viewport meta tag?