Getting transparency for multi-band GeoTIFF in OpenLayers

Using this 3-band GeoTIFF:

Driver: GTiff/GeoTIFFFiles: mb_p_cr.tif       mb_p_cr.tif.ovrSize is 6196, 8003Coordinate System is:GEOGCRS["WGS 84",    DATUM["World Geodetic System 1984",        ELLIPSOID["WGS 84",6378137,298.257223563,            LENGTHUNIT["metre",1]]],    PRIMEM["Greenwich",0,        ANGLEUNIT["degree",0.0174532925199433]],    CS[ellipsoidal,2],        AXIS["geodetic latitude (Lat)",north,            ORDER[1],            ANGLEUNIT["degree",0.0174532925199433]],        AXIS["geodetic longitude (Lon)",east,            ORDER[2],            ANGLEUNIT["degree",0.0174532925199433]],    ID["EPSG",4326]]Data axis to CRS axis mapping: 2,1Origin = (-83.175514742389765,-4.909911889634341)Pixel Size = (0.001837484779547,-0.001807935284019)Metadata:  AREA_OR_POINT=AreaImage Structure Metadata:  INTERLEAVE=PIXELCorner Coordinates:Upper Left  ( -83.1755147,  -4.9099119) ( 83d10'31.85"W,  4d54'35.68"S)Lower Left  ( -83.1755147, -19.3788180) ( 83d10'31.85"W, 19d22'43.74"S)Upper Right ( -71.7904590,  -4.9099119) ( 71d47'25.65"W,  4d54'35.68"S)Lower Right ( -71.7904590, -19.3788180) ( 71d47'25.65"W, 19d22'43.74"S)Center      ( -77.4829869, -12.1443649) ( 77d28'58.75"W, 12d 8'39.71"S)Band 1 Block=6196x1 Type=Byte, ColorInterp=Red    Computed Min/Max=0.000,255.000  Minimum=0.000, Maximum=255.000, Mean=1.252, StdDev=12.524  Overviews: 3098x4002, 1549x2001, 775x1001, 388x501, 194x251  Metadata:    STATISTICS_MAXIMUM=255    STATISTICS_MEAN=1.2524864788035    STATISTICS_MINIMUM=0    STATISTICS_STDDEV=12.523906791266    STATISTICS_VALID_PERCENT=100Band 2 Block=6196x1 Type=Byte, ColorInterp=Green    Computed Min/Max=0.000,255.000  Minimum=0.000, Maximum=255.000, Mean=1.538, StdDev=15.985  Overviews: 3098x4002, 1549x2001, 775x1001, 388x501, 194x251  Metadata:    STATISTICS_MAXIMUM=255    STATISTICS_MEAN=1.5377140689737    STATISTICS_MINIMUM=0    STATISTICS_STDDEV=15.98530773052    STATISTICS_VALID_PERCENT=100Band 3 Block=6196x1 Type=Byte, ColorInterp=Blue    Computed Min/Max=0.000,255.000  Minimum=0.000, Maximum=255.000, Mean=1.856, StdDev=17.187  Overviews: 3098x4002, 1549x2001, 775x1001, 388x501, 194x251  Metadata:    STATISTICS_MAXIMUM=255    STATISTICS_MEAN=1.8563095125642    STATISTICS_MINIMUM=0    STATISTICS_STDDEV=17.187388492599    STATISTICS_VALID_PERCENT=100

how can the following OpenLayers call be modified to get transparency?

new WebGLTileLayer({  style: relief,  source: new GeoTIFF({    sources: [{      url: 'raster/mb_p_cr.tif',      overviews: ['raster/mb_p_cr.tif.ovr'],    }],  }),}),

As it is, it displays a black background:

Using the following OL styling is not enough (or correct?):

const relief = {  color: ['case',    ['>', ['band', 4], 0],    [0, 0, 0, 0.0],  ],};

and this way does not work either:

const relief = {  color: ['case',    ['all',      ['==', ['band', 1], 0],      ['==', ['band', 2], 0],      ['==', ['band', 3], 0],      ['==', ['band', 4], 1],    ],    [0, 0, 0, 0.0],    ['color',      ['*', ['band', 1], 255],      ['*', ['band', 2], 255],      ['*', ['band', 3], 255],      ['band', 4],    ],  ],};

Unfortunately, including convertToRGB: true to the OL call and assigning nodata: 0 to the GeoTIFF were not enough. For some reason that cannot be discovered yet, the GeoTIFF dissapeared after several tests and now Chrome's console says:

GET http://localhost:5173/raster/.test/mb_p_cr.tif 416 (Range Not Satisfiable)Promise.then (async)        (anonymous) @   main.js:582Show 13 more frames

Any clues? any hint is very welcomed,