L7file = system.file("tif/L7_ETMs.tif", package = "stars")
L7 = read_stars(L7file)

### working but gives warning
tm_shape(L7) + 
   tm_raster(3, 2, 1)

# Warning message:
# In value[[3L]](cond) : could not rename the data.table

### not working gives error
tm_shape(L7) + 
   tm_rgb(3, 2, 1)

# Error: palette should be a character value
# In addition: Warning message:
# In value[[3L]](cond) : could not rename the data.table