https://github.com/harfbuzz/harfbuzz/tree/11.2.1

User Manual
https://harfbuzz.github.io/

hb-shape  unifont-16.0.04.otf "नमस्ते"
hb-shape  unifont-16.0.04.otf "नमस्ते"  --no-glyph-names --show-extents  --output-format=json 

[
{"g":2345,"cl":0,"dx":0,"dy":0,"ax":64,"ay":0,"xb":0,"yb":44,"w":64,"h":-40},
{"g":2351,"cl":1,"dx":0,"dy":0,"ax":64,"ay":0,"xb":0,"yb":44,"w":64,"h":-40},
{"g":2361,"cl":2,"dx":0,"dy":0,"ax":64,"ay":0,"xb":0,"yb":44,"w":64,"h":-40},
{"g":2382,"cl":2,"dx":0,"dy":0,"ax":0,"ay":0,"xb":-28,"yb":4,"w":16,"h":-12},
{"g":2341,"cl":4,"dx":0,"dy":0,"ax":64,"ay":0,"xb":0,"yb":44,"w":64,"h":-40},
{"g":2376,"cl":4,"dx":0,"dy":0,"ax":0,"ay":0,"xb":-52,"yb":56,"w":24,"h":-12}
]



hb-view  unifont-16.0.04.otf "नमस्ते"

~/git/bdf2ttf/bdf2ttf -v unifont.ttf ~/git/bdf2ttf/sample.ini ../bdf/unifont.bdf
hb-shape  unifont.ttf "नमस्ते"  --no-glyph-names --show-extents  --output-format=json 


hb-shape  unifont-15.1.05.otf "नमस्ते"  --font-size=16 --output-format=json > test.json
[
{"g":"gid2345","cl":0,"dx":0,"dy":0,"ax":16,"ay":0},
{"g":"gid2351","cl":1,"dx":0,"dy":0,"ax":16,"ay":0},
{"g":"gid2361","cl":2,"dx":0,"dy":0,"ax":16,"ay":0},
{"g":"gid2382","cl":2,"dx":0,"dy":0,"ax":0,"ay":0},
{"g":"gid2341","cl":4,"dx":0,"dy":0,"ax":16,"ay":0},
{"g":"gid2376","cl":4,"dx":0,"dy":0,"ax":0,"ay":0}
]
static const unsigned char teststr[] U8X8_PROGMEM = {
  0x09, 0x28, 0x00, 0x00, // u8g2_DrawGlyph(&u8g2, 0, 0, 2344);
  0x09, 0x2e, 0x10, 0x00, // u8g2_DrawGlyph(&u8g2, 16, 0, 2350);
  0x09, 0x38, 0x10, 0x00, // u8g2_DrawGlyph(&u8g2, 32, 0, 2360);
  0x09, 0x4d, 0x00, 0x00, // u8g2_DrawGlyph(&u8g2, 32, 0, 2381);
  0x09, 0x24, 0x10, 0x00, // u8g2_DrawGlyph(&u8g2, 48, 0, 2340);
  0x09, 0x47, 0x00, 0x00, // u8g2_DrawGlyph(&u8g2, 48, 0, 2375);
  0x00, 0x00  // end of binary
};


Further tests:
https://github.com/olikraus/u8g2/issues/1015
അഷ്ഹദ്
static const unsigned char testarabic[] U8X8_PROGMEM = {
  0x0d, 0x05, 0x00, 0x00, // u8g2_DrawGlyph(&u8g2, 0, 0, 3333);
  0x0d, 0x37, 0x10, 0x00, // u8g2_DrawGlyph(&u8g2, 16, 0, 3383);
  0x0d, 0x4d, 0x00, 0x00, // u8g2_DrawGlyph(&u8g2, 16, 0, 3405);
  0x0d, 0x39, 0x10, 0x00, // u8g2_DrawGlyph(&u8g2, 32, 0, 3385);
  0x0d, 0x26, 0x10, 0x00, // u8g2_DrawGlyph(&u8g2, 48, 0, 3366);
  0x0d, 0x4d, 0x00, 0x00, // u8g2_DrawGlyph(&u8g2, 48, 0, 3405);
  0x00, 0x00  // end of binary
};


https://github.com/olikraus/u8g2/issues/640
String msg = "ﺍﻟﺸُﻮﻛُﻮﻻَﺗَﺔ أﻭ ﺍﻟﺸُﻜُﻮﻻَﺗَﺔ أﻭ ﺍﻟﺸِﻴﻜُﻮﻻَﺗَﺔ أﻭ ﺍﻟﺸﻮﻛﻮﻻ أﻭ ﺍﻟﺸﻜﻼﻁ"; 
//String msg = "Hello world! This is a test string.";


arabic "Hello World", u8g2_font_unifont_t_arabic

مرحبًا
static const unsigned char testarabic[] U8X8_PROGMEM = {
  0x06, 0x27, 0x00, 0x00, // u8g2_DrawGlyph(&u8g2, 0, 0, 1575);
  0x06, 0x28, 0x08, 0x00, // u8g2_DrawGlyph(&u8g2, 8, 0, 1576);
  0x06, 0x4b, 0x00, 0x00, // u8g2_DrawGlyph(&u8g2, 8, 0, 1611);
  0x06, 0x2d, 0x08, 0x00, // u8g2_DrawGlyph(&u8g2, 16, 0, 1581);
  0x06, 0x31, 0x08, 0x00, // u8g2_DrawGlyph(&u8g2, 24, 0, 1585);
  0x06, 0x45, 0x08, 0x00, // u8g2_DrawGlyph(&u8g2, 32, 0, 1605);
  0x00, 0x00  // end of binary
};


hb-shape  unifont-15.1.05.otf "नमस्ते"  --font-size=16 --output-format=json | ./hbshape2u8g2 "नमस्ते" teststr 
static const unsigned char teststr[] U8X8_PROGMEM = {  // "नमस्ते"
  0x09, 0x28, 0x00, 0x00, // u8g2_DrawGlyph(&u8g2, 0, 0, 2344);
  0x09, 0x2e, 0x10, 0x00, // u8g2_DrawGlyph(&u8g2, 16, 0, 2350);
  0x09, 0x38, 0x10, 0x00, // u8g2_DrawGlyph(&u8g2, 32, 0, 2360);
  0x09, 0x4d, 0x00, 0x00, // u8g2_DrawGlyph(&u8g2, 32, 0, 2381);
  0x09, 0x24, 0x10, 0x00, // u8g2_DrawGlyph(&u8g2, 48, 0, 2340);
  0x09, 0x47, 0x00, 0x00, // u8g2_DrawGlyph(&u8g2, 48, 0, 2375);
  0x00, 0x00  // end of binary
};