I had fun today installing a Walksnail HD KIT V2 (4:3 camera) in my Flight Cub Proton 5/6" quad. Hopefully that was not a really dumb thing to do...
The FC is a Heliospring F3/F4 running Emuflight 0.4.2 The Emuflight Configurator 0.4.1 UARTS don't have the VTX(MSP+Displayport) option. Is there a CLI command that will provide that like can be done with Betaflight? Also the Video Format selection in the OSD Tab only has Auto, PAL, or NTSC, there is no HD option. Can I make the OSD Font HD size or fit correctly without that option?

Unfortunately I think you might be out of luck. EmuFlight has been pretty much abandoned with no major feature releases for 18 months. There have been a couple of minor updates this year to fix some outstanding bugs and to support some additional gyros, but that is all. There is an unstable DEV release at the link below which has some OSD enhancements but it specifically calls out HDZero, so I'm not sure if it will work for the DJI or Walksnail systems. I guess you have nothing to lose by trying that version to see what gives, but just be aware that it's an unstable release which isn't fully tested so it could have some undesirable bugs in it.

• EmuFlight Unstable Dev Build 2666: https://github.com/emuflight/dev-unstabl...171109-hex
  
• EmuFlight Configurator Unstable Dev Build 767: https://github.com/emuflight/dev-unstabl...164604-cfg
  

I may be in luck (if it works re stability) down the GitHub page it says "this works for Walksnail; set as PAL for proper OSD alignment" is says also that it does not work with DJI fully. One week old!

I may be a bit out of my depth here. I followed your links and see Assets listed for my FC and the Configurator, but they still have the old number designations. 0.4.2 for the FC and 0.4.1 for the Configurator. Are these "Assets" the old stable ones or the new ones with the modifications (test code?) inserted? I am unsure if I am downloading and installing the correct stuff. Do I replace the configurator 0.4.1 with this unstable version or should I keep both?

I completely missed the information stating that those dev builds supported Walksnail and the WTFOS enabled DJI FPV System V1 (and limited functionality on the DJI O3 system), so that's good news. It seems a bit odd that nerdCopter opted to specifically label everything with "HDZero" rather than just a generic "HD" label if it works for all.

Those hex files are a development build of the 0.4.2 firmware with additional code added to support the OSD changes. So you just need to flash the EmuFlight_0.4.2_HELIOSPRING_Build_2666_eaddecec0.hex file to your FC using the dev build of the EnuFlight Configurator.

I don't run macOS so I'm not sure if installing the dev version of the emuflight-configurator_0.4.1_macOS.dmg file will overwrite the already installed version or if it will install a side-by-side version. Either way, you probably won't have any choice, so just install it and see what happens. If it does overwrite the original (non-dev) version of EmuFlight Configurator and you need to go back to the previous release version for any reason, you will just have to uninstall the dev version and reinstall the release version again.

OK great, the numbers didn't change in the "development build". FWIW since the numbers didn't change macOS sees them same and asks if I want to overwrite or install side by side, I'll have to keep them seperate myself, no biggie.

I used the modified Emuflight configurator to flash the modified firmware. This gave me new selections in the Ports and OSD tabs. I selected MSP+Displayport in the Ports Tab under Peripherals. I also turned on Configuration/MSP (I'm using UART1) but every time I hit Save and Reboot it would hang up, After cycling power the button under Configuration/MSP would be off again. So I can't get that to stay ON. If I only selected MSP+Displayport it would reboot. In the OSD tab HD was selectable and gave me an HD screen to drag and drop OSD items in. But I was never able to see anything in the goggles. No FC data is being sent to the goggles. Maybe this is because I have not set up anything in the Analog VTX tab? Bummer.

To cheer myself up I installed a Walksnail Avatar HD Mini 1s Lite Kit in my BetaFPV HX115 SE, a 3" toothpick powered by a 2s 450 mAh LiPo. After wiring the unit I went into Betaflight, selected an Avatar Preset, and checked that Configuration+MSP was ON and VTX(MSP+Displayport) was selected in the Ports tab for the correct UART. Then I put my goggles on and dragged the items around in the OSD tab (HD) until I was happy. Then I took it outside for a flight. So that went extremely well

Maybe I missed a step with the Emuflight set up. Not being able to turn Configuration/MSP ON is a red flag. Certainly there's no Preset like in Betaflight. Or maybe I got my wires crossed. I'll have another look tomorrow at both the physical wiring and the possibility of loading Analog VTX tables even though I'm using Walksnail HD. If anyone has a suggestion I am all ears

Not being to see OSD elements on the screen will be because you're not able to set "MSP Display Port" as the Peripherals option for the port. You don't need VTX tables configured for that.

I just flashed the dev build of the EmuFlight 0.4.2 firmware to a spare Holybro Kakute F7 that I have in my parts box and I am able to set the "MSP Display Port" option for any of the ports. The setting persists and the FC reboots without any issues. I'm obviously not able to confirm if any OSD elements display on the screen as the FC isn't connected to a VTX or anything else, but I'm sure that with the "MSP Display Port" option set and persisted it would work as expected.

When you flash new firmware to the FC, make sure you have the "Full chip erase" option switched on. When you set "MSP Display Port" as the Peripherals option for UART1, make sure no other option is switched on for the port. You don't need to switch on the Configuration/MSP option. Just setting the Peripherals option to be "MSP Display Port" is all that is required. If that still doesn't work, try using a different spare UART.

Got it. I don't need to switch on the Configuration/MSP option, good, because that is what doesn't "stick". And I don't need VTX tables.
I'll do the other things you mentioned as well.

Success! Storytime...
First, there is this note on the Ports Tab in Emuflight:
"...not all combinations are valid. When the flight controller firmware detects this the serial port configuration will be reset. Note: Do NOT disable MSP on the first serial port unless you know what you are doing..."
That didn't mean anything to me before but maybe it does now, LOL.
I reflashed with "Full Chip Erase" for a fresh start and selected just "MSP+Displayport" on UART1. As before the Save and Reboot sequence failed. Also no OSD. So I moved the VTX connections to UART5. I reflashed for good measure, selected "MSP+Displayport" for UART5 and the Save and Reboot sequence worked normally. I selected HD on the OSD page and grabbed my goggles and voila! A normal OSD display with all the elements I wanted.
That made me very happy Of course then I had to load my diff all and do the Emuflight set up again but it was quick. And there was no glitchy hanging up that I had yesterday with the configurator. I believe that was all down to me trying to use MSP+Displayport on UART1. Who knew?
I will try to notify the Emuflight Developer that his efforts are much appreciated (if I can figure out how).
And again thank you so much for helping me with this puzzle, great sport, eh? Cheers!

No problem. I'm glad it's now working without issues. At some point I'm sure those changes will make it into an official EmuFlight release, so just make sure you keep periodically checking the EmuFlight GitHub releases page.

I got a few flights in with the Emuflight HD OSD working just fine but today while flying I realized the Betaflight OSD had frozen. After landing and cycling power to the quad the BF OSD was still frozen with the same info as the previous flight, kinda funny. Then after cycling power to both the Tx and quad a little while later I had no BF OSD. Returning home I looked for loose wires and decided to try powering up again, lo and behold the BF OSD was back But after arming the quad it froze again, the timer 2 didn't even start when I armed the quad. I guess I found a glitch in this new development build.