Replying to myself here...I have my Ender 3 Pro with 4.2.7 board and 1.3 BLTouch working.
For those who may follow...
Put the 3-pin BLT connector into the BLT connector on the 4.2.7 board, on the left side. You will likely have to swap the blue and red wires to match the pinout on the 4.2.7 board connector (I did).
Then remove the -Z limit switch connector from the board, and put the 2-pin BLT connector into the -Z limit switch connector on the board.
So, yes -- part of the BLT is plugged into the BLT connector on the board, and part is plugged into the -Z limit switch connector.
Then use the firmware from here:
https://github.com/Flawioo/Creality-Ender-3-board-v4.2.7/blob/master/firmware-20200825-161146-BLT-and_Runnout-filament.bin
Flash the firmware, boot it up, set the z-offset, and you're off and running.
Bit thanks to Flavio (whose github repository for the firmware .bin file is linked above), who helped me work through using the -z limit switch connector for the BLT to get it all working.
I'm printing and auto-bed-leveling on the Ender 3 Pro with 4.2.7 board now. All good.
Hopefully Creality will release a firmware version that works correctly soon, but until then, the Marlin 2.0.6 version above is the way to go.

@SlackHacky thanks for the info, I've tried Creality's official firmware with a 1.3.1 BLTouch and a 4.2.7 board (tried using both the adapter block for the display and the BLTouch port on the board) -- neither works.
Do you have a link to a .bin file for the complied bugfix206 you mentioned? Or a link to where I can get it?
Thanks!

I have an Ender 3 Pro. I upgraded to the 32-bit board, version 4.2.7, last week. It came with the firmware pre-flashed, and it worked without any problems.
I received a BLTouch v1 today - an officially labeled and branded Creality version. Flashed the firmware recommended ( 4.2.7V-Ender-3 Pro-32bit Mainboard-Marlin2.0.1-V1.3.1-BLTouch-TMC2225.bin). Before wiring up the BLTouch, the machine booted but the buzzer is on constantly.
Tried both methods of connecting: first I used the adapter block for the display port included with the BLTouch v1, removing the Z-axis switch, and plugging the BLTouch into the adapter board. The display would not come on.
Tried the wiring above, using the BLTouch port on the 4.2.7 board, swapping the blue and red wires in the black 3-pin BLTouch connector and trimming the 2-pin connector so it fits in the BLTouch port on the board. In that configuration, the machine boots, the BLTouch initializes (red light, pin pops in and out a couple of times). But when I do an Auto Home, the machine starts to Auto Home, then moves to the center of the build plate, and displays "STOPPED" on the display. And the buzzer is on constantly again.
I would sure appreciate some help getting this working. The worst part is that I can't just unplug the BLTouch and re-flash the 32-bit 4.2.7 non-BLTouch firmware -- it's not available on Creality's site.
Thanks in advance for any help.