i saw this https://rotorbuilds.com/build/10984 the poormansfatshark. i didnt build but was a pleasure to see this possibility
i thougt probably wireless openfield-betaflight-raspi is intresting to someone:

Raspberrypi (single-board computer, size of a creditcard) openfield betaflight (and blheli suite) using Raspberrypi as a wireless betaflight „adapter“

I dont now are there other small portable options for blheli on the field, possibly this is intressting for someone. The only unique feature for betaflight in the field, when its prepared for controll wireless, its able to controll it from everywhere over internet, as example with realvnc, teamviewer... someone far away could help see your flight log, setup pid... Its able to controll raspberrypi-betaflight with m“any“ platform; windows, android, ios... tablet, smartphone

the most other openfield possibilities like speedybee-adapter would be more easy to prepare and use and cost less. one thing i like is; a raspberrypi can fly as a quad too, its "usable" as a flightcontroller

when everything is build, on the field you have to open a hotspot, plug in the powerbank, connect probably with smartphone and vnc, start betaflight on it, connect the fc...

What you need to build

-some time
-raspberrypi p3b
-beeing intressted about install a system on a single-board computer and set it up
-sd-card at least 4gb
-display able to connect with hdmi
-hdmi cable
-a computer for preparing the sd card
-some software

Additional hardware for use wireless in the field

-something to make a hotspot for raspberry
-something where realvnc (or another application) is prepared; tablet, smartphone..
-powerbank and micro usb cable to power the raspberrypi (or there would be possibilities over a 5vbec and a lipo)
-a second cable to connect the quad to raspberry
(like the description in the video from quadframesuk, the other possibility would be to controll it with raspberry with a wire hdmi-display, hdmi cable, mouse and keyboard (enogh resolution, my 800x480 7“ touch display doesnt work because of the betaflight program scale, i couldnt see the hole betaflight program window at one time, it wasnt handy to move the window around, but possibly theres a reason, i couldnt find) )

There is a tutorial from QuadFramesUK:
copypaste from there;

Part 1 Raspberry Pi 3 B (OS Flash & Basic Setup)

Part 2 How To Install Betaflight Configurator onto Raspberry Pi

Part 3 Raspberry Pi - Butterflight Installation
Part 4 Raspberry Pi - Blheli Installation

Hardware Required 1. PC / Laptop 2. Raspberry Pi B 3 pre-installed with Raspian 5. HDMI Monitor 6. HDMI Lead 7. USB Mouse 8. USB Keyboard 9. Micro USB Lead

Software Needed for Part 1

1. SD Card Formatter https://www.sdcard.org/downloads/form... 2. Etcher https://etcher.io/ 3. Raspian Stretch with desktop OS
   https://www.raspberrypi.org/downloads...
   Software Needed for Part 2
2. Betaflight Configurator (Source Code Zip) https://github.com/betaflight/betafli... 2. nw.js-armv7-binaries (not the SDK version) https://github.com/LeonardLaszlo/nw.j... linux-arm.tar.gz Terminal Commands to copy and paste (versions numbers of Betaflight Configurator & armv7-binaries will depend on the version that you choose to download. you will need to change the version numbers in the related commands below as described in the video. Link to download .TXT commands file for copy & Paste https://1drv.ms/t/s!AqYE1MiwHVxs5WL5A...

hope someone enjoy or give it a try