Edited Nov 2021: Typo and text cleanup. Added probe XY offset determination method using a graph paper. Added video by Ken Sansilo showing the probe in use.

Credit for this inspiration goes to Derokero, https://www.thingiverse.com/thing:4111545

Here's a video by Ken Sanislo showing it in use.
https://www.youtube.com/watch?v=Bhk3W916WUE

This is adapter is for an AnyCubic Mega Zero printer using the supplied 2.4mm Allen-key on a SKR 1.4 Turbo board. Microswitch is wired to the servo probe port. It should work on the stock controller board but you will need to edit the configuration to remove some features to release memory space for mesh levelling.

Deviation test gave 0.001739. Not too shabby for a 20c microswitch.

Marlin Configuration.h settings:

DEFINE AUTO_BED_LEVELING_BILINEAR

DEFINE FIX_MOUNTED_PROBE

• To automatically reload bed mesh data is reloaded after G28

  define RESTORE_LEVELING_AFTER_G28

define LCD_BED_LEVELING

// Useful to do an initial bed level

define LEVEL_BED_CORNERS

if ENABLED(LEVEL_BED_CORNERS)

define LEVEL_CORNERS_INSET 15 // (mm) An inset for corner leveling

define LEVEL_CORNERS_Z_HOP 5.0 // (mm) Move nozzle up between corners

define LEVEL_CORNERS_HEIGHT 0.0 // (mm) Z height of nozzle at leveling points

define LEVEL_CENTER_TOO // Move to the center after the last corner - this is optional if you use an even grid which does not read the center.

endif

// 5x5 points, 4x4 or 3x3 works, use higher if bed is uneven

define GRID_MAX_POINTS_X 5

Disable this if you use the dedicated PROBE connection

define Z_MIN_PROBE_USES_Z_MIN_ENDSTOP_PIN

If you don't have a dedicated PROBE port. You can either wire the switch (use Normally Closed NC connection) in series with the Z Limit switch. For this config, enable this.

define Z_MIN_PROBE_USES_Z_MIN_ENDSTOP_PIN

//These are for my printer, you will need to measure this on your printer

define NOZZLE_TO_PROBE_OFFSET { -38, 0.5, -1.5 }

// I find it easiest to use a piece of graph paper on a writing pad. Align the paper to the bed X and Y axis.

Lower the nozzle onto a co-ordinate point to mark the position. Lower the probe and press it onto the paper. You can now read off the X and Y the offsets.

Change as preferred.

define MIN_PROBE_EDGE 5

// Optional, increases accuracy.

define MULTIPLE_PROBING 2

// These work on my printer using the supplied 2.4mm allen key. Will be different if your allen key differs.

define Z_CLEARANCE_DEPLOY_PROBE 10 // Z Clearance for Deploy/Stow

define Z_CLEARANCE_BETWEEN_PROBES 3 // Z Clearance between probe points

define Z_CLEARANCE_MULTI_PROBE 2 // Z Clearance between multiple probes

define Z_AFTER_PROBING 5 // Z position after probing is done

// For M851 give a range for adjusting the Z probe offset

define Z_PROBE_OFFSET_RANGE_MIN -20

define Z_PROBE_OFFSET_RANGE_MAX 20

// Before deploy/stow pause for user confirmation.
// Pauses for you to deploy/stow the allen key.
// WARNING: DO NOT OMIT this.

define PAUSE_BEFORE_DEPLOY_STOW

Marline configuration_adv.h settings:

// Useful to adjust the Z for the first layer.
// Note that this feature is not available on A4988 drivers.

define BABYSTEPPING

define BABYSTEP_ZPROBE_OFFSET

Add this line to your slicer to load the leveling mesh before start of print.
M420 S1