In my DSLR days I recommend the D500 (for less $ a D7200) and Tamron 150-600 G2 or Sigma 150-600 sport to a lot of newcomers that were parts of birding trips or classes I lead and for some that is still a good choice if willing to buy a used D500.The demise of Dx is more an issue when it comes to attracting new users to bird photography. just look at the price difference of a D500 + 500pf vs a z8 + 800pf. Neither are / were cheap but the step up is now significant. For wildlife, DX was a more convenient and affordable entry drug to later upgrade from. At the time DX also allowed for faster frame rates (unless you added the grip and pro batteries to the D850) and I expect the equivalent today would be rolling shutter (should be lower on DX than FX for the same pixel density). If one can afford a z8 and 800pf, the point is indeed moot but the hobby has become outrageous and FX only is not helping new users to jump in.
My wife used a Z50 with adapted f mount lenses the Tamron 18-400 until she moved to a Z7II and Z400 f/4.5 since replaced with the Z28-400 that set up is quite light and versatile for her and her bad back and arthritis. Recent price drops on the Z7II have put her set up in reach of more birders.
Shortly after I got into photography the D300s was my first Nikon body coming from a Canon Rebel borrowed from my wife (who has been in photography since 1975). Then the D500 came out and over time we bought three two for me and one for my wife I used one with a battery grip, balanced well with my longer and heavier lenses, and one without a grip with the Tamron 18-400 that I took out chasing chukars and following my gun hunting and falconry friends around in the steep and rugged mountains and canyons in Idaho and Oregon.
I did add the grip to my D850 and the adapter door for the EN-El 18 batteries used in my D4s and later D6. For me the grip was a no brainer since I already had batteries and they became interchangeable with my other body. Since I had made the investment in D850 the grip and big battery = higher frame rates was the beginning of the end for my D500. My birding lenses back then were Tamron 150-600 G2 a Sigma 150-600 sport, a Tamron 18-400 (way better than it should have been) and a Nikon 200-500 nice lens but my copy was a lemon and went back and forth to Nikon 3 times before it go fixed and sold because it made me nervous. At the end of my DSLR the 500 pf was added and a then got a great buy from Nikon USA on a refurbished 600 mm f/4E to go along with my D6. Yup it got spendy even back in the DSLR days.
Now my primary birding rigs are 2 Z9's, a Z6III and Z800 and 600 pf and z mount Tamron 150-500. So no not cheap but funded by selling off all my DSLR and f mount glass by 6-22 before the used prices started dropping like a rock.