[Samsung Gear S3] parasetam0l:
Thank you all for your good wishes. It's been a busy week for me.

UPDATE:

I built hwcomposer and gralloc from stratch. Now android recognizes our display.

11-14 01:04:46.884 1956 1956 D hwcomposer: using
11-14 01:04:46.884 1956 1956 D hwcomposer: xres = 360 px
11-14 01:04:46.884 1956 1956 D hwcomposer: yres = 360 px
11-14 01:04:46.884 1956 1956 D hwcomposer: width = 33 mm (277.090000 dpi)
11-14 01:04:46.884 1956 1956 D hwcomposer: height = 33 mm (277.090000 dpi)
11-14 01:04:46.884 1956 1956 D hwcomposer: refresh rate = 56 Hz
11-14 01:04:46.884 1956 1956 V DisplayResourceManagerModule: externalMPP type(4), index(0)
11-14 01:04:46.884 1956 1956 I hwcutils: Open /dev/s5p-smem
11-14 01:04:46.885 1956 1956 V DisplayResourceManagerModule: externalMPP type(5), index(0)
11-14 01:04:46.886 1956 1956 I hwcomposer: PSR info devname = /sys/devices/14830000.decon_fb/psr_info
11-14 01:04:46.886 1956 1956 I hwcomposer: PSR mode = 2 (0: video mode, 1: DP PSR mode, 2: MIPI-DSI command mode)
11-14 01:04:46.886 1956 1956 I hwcomposer: Panel type = 0 (0: Legacy, 1: DSC)
11-14 01:04:46.886 1976 1976 I SurfaceFlinger: Using HWComposer service: 'default'
11-14 01:04:46.888 1956 1956 I HWC2On1Adapter: Found support for HWC virtual displays
11-14 01:04:46.889 1976 1976 I SurfaceFlinger: SurfaceFlinger is starting
11-14 01:04:46.889 1956 1956 E HWC2On1Adapter: Setting active config to 0 for HWC1 config 0

11-14 01:04:54.226 1976 1976 I RenderEngine: OpenGL ES informations:
11-14 01:04:54.226 1976 1976 I RenderEngine: vendor : ARM
11-14 01:04:54.226 1976 1976 I RenderEngine: renderer : Mali-T720
11-14 01:04:54.226 1976 1976 I RenderEngine: version : OpenGL ES 3.1 v1.r29p0-01rel0.###other-sha0123456789ABCDEF0###
11-14 01:04:54.226 1976 1976 I RenderEngine: extensions: GL_EXT_debug_marker GL_ARM_rgba8 GL_ARM_mali_shader_binary GL_OES_depth24 GL_OES_depth_texture GL_OES_depth_texture_cube_map GL_OES_packed_depth_stencil GL_OES_rgb8_rgba8 GL_EXT_read_format_bgra GL_OES_compressed_paletted_texture GL_OES_compressed_ETC1_RGB8_texture GL_OES_standard_derivatives GL_OES_EGL_image GL_OES_EGL_image_external GL_OES_EGL_image_external_essl3 GL_OES_EGL_sync GL_OES_texture_npot GL_OES_vertex_half_float GL_OES_required_internalformat GL_OES_vertex_array_object GL_OES_mapbuffer GL_EXT_texture_format_BGRA8888 GL_EXT_texture_rg GL_EXT_texture_type_2_10_10_10_REV GL_OES_fbo_render_mipmap GL_OES_element_index_uint GL_EXT_shadow_samplers GL_OES_texture_compression_astc GL_KHR_texture_compression_astc_ldr GL_KHR_texture_compression_astc_hdr GL_KHR_texture_compression_astc_sliced_3d GL_KHR_debug GL_EXT_occlusion_query_boolean GL_EXT_disjoint_timer_query GL_EXT_blend_minmax GL_EXT_discard_framebuffer GL_OES_get_program_binary GL_OES_texture_3D GL_EXT_texture_storage GL_EXT_multisamp
11-14 01:04:54.226 1976 1976 I RenderEngine: GL_MAX_TEXTURE_SIZE = 8192
11-14 01:04:54.226 1976 1976 I RenderEngine: GL_MAX_VIEWPORT_DIMS = 8192

BUT:

11-14 01:04:57.239 1976 1976 E HWComposer: loadLayerMetadataSupport: getLayerGenericMetadataKeys failed: UNSUPPORTED (8)
11-14 01:04:57.242 1976 1976 I HWComposer: Switching to legacy multi-display mode
11-14 01:04:57.242 1976 1976 E HWComposer: isConnected failed for display 0: Invalid display
11-14 01:04:57.243 1956 2065 E display : [PrimaryDisplay] unknown display attribute 7
11-14 01:04:57.243 1956 2065 E display : [PrimaryDisplay] unknown display attribute 8
11-14 01:04:57.243 1956 2065 E display : [PrimaryDisplay] unknown display attribute 9
11-14 01:04:57.243 1956 2065 E display : [PrimaryDisplay] unknown display attribute 10
11-14 01:04:57.243 1956 2065 E display : [PrimaryDisplay] unknown display attribute 11
11-14 01:04:57.243 1956 2065 E display : [PrimaryDisplay] unknown display attribute 12
11-14 01:04:57.248 1976 2142 W SurfaceFlinger: Ignoring VSYNC request while display is disconnected
11-14 01:04:57.249 1976 2142 W SurfaceFlinger: Ignoring VSYNC request while display is disconnected
11-14 01:04:57.249 1976 2143 W SurfaceFlinger: Ignoring VSYNC request while display is disconnected
11-14 01:04:57.249 1976 2143 W SurfaceFlinger: Ignoring VSYNC request while display is disconnected
11-14 01:04:57.250 1976 2142 W SurfaceFlinger: Ignoring VSYNC request while display is disconnected
11-14 01:04:57.250 1976 2142 W SurfaceFlinger: Ignoring VSYNC request while display is disconnected
11-14 01:04:57.250 1976 1976 E HWComposer: getDisplayConnectionType: getDisplayConnectionType failed for display 0: Unsupported (8)
11-14 01:04:57.254 1976 1976 I FramebufferSurface: framebuffer size has been limited to [360x360] from [360x360]
11-14 01:04:58.099 1976 1976 D SurfaceFlinger: Setting power mode 2 on display 0
11-14 01:04:58.099 1956 2065 I hwcomposer: exynos_setPowerMode:: disp(0), mode(2)
11-14 01:04:58.100 1976 1976 D SurfaceFlinger: Finished setting power mode 2 on display 0

This means we still have incompatibility between hwcomposer and android system. I am missing something. I will double check framebuffer and display permissions. And I also noticed that surfaceflinger from Exynos7570 device uses this libraries.

solis:/system_root/system/bin # readelf -d surfaceflingerj4lte | grep NEEDED
0x00000001 (NEEDED) Shared library: [android.frameworks.displayservice@1.0.so]
0x00000001 (NEEDED) Shared library: [android.hardware.configstore-utils.so]
0x00000001 (NEEDED) Shared library: [android.hardware.configstore@1.0.so]
0x00000001 (NEEDED) Shared library: [vendor.samsung_slsi.hardware.configstore-utils.so]
0x00000001 (NEEDED) Shared library: [vendor.samsung_slsi.hardware.configstore@1.0.so]
0x00000001 (NEEDED) Shared library: [android.hardware.graphics.allocator@2.0.so]
0x00000001 (NEEDED) Shared library: [android.hardware.graphics.allocator@3.0.so]
0x00000001 (NEEDED) Shared library: [vendor.samsung_slsi.hardware.ExynosHWCServiceTW@1.0.so]
0x00000001 (NEEDED) Shared library: [libbinder.so]
0x00000001 (NEEDED) Shared library: [libcutils.so]
0x00000001 (NEEDED) Shared library: [libdisplayservicehidl.so]
0x00000001 (NEEDED) Shared library: [libhidlbase.so]
0x00000001 (NEEDED) Shared library: [libhidltransport.so]
0x00000001 (NEEDED) Shared library: [libinput.so]
0x00000001 (NEEDED) Shared library: [liblayers_proto.so]
0x00000001 (NEEDED) Shared library: [liblog.so]
0x00000001 (NEEDED) Shared library: [libprocessgroup.so]
0x00000001 (NEEDED) Shared library: [libsync.so]
0x00000001 (NEEDED) Shared library: [libtimestats_proto.so]
0x00000001 (NEEDED) Shared library: [libutils.so]
0x00000001 (NEEDED) Shared library: [libsurfaceflinger.so]
0x00000001 (NEEDED) Shared library: [libSurfaceFlingerProp.so]
0x00000001 (NEEDED) Shared library: [libc++.so]
0x00000001 (NEEDED) Shared library: [libc.so]
0x00000001 (NEEDED) Shared library: [libm.so]
0x00000001 (NEEDED) Shared library: [libdl.so]

But newly compiled one uses

solis:/system_root/system/bin # readelf -d surfaceflinger | grep NEEDED
0x00000001 (NEEDED) Shared library: [android.frameworks.displayservice@1.0.so]
0x00000001 (NEEDED) Shared library: [android.hardware.configstore-utils.so]
0x00000001 (NEEDED) Shared library: [android.hardware.configstore@1.0.so]
0x00000001 (NEEDED) Shared library: [android.hardware.graphics.allocator@2.0.so]
0x00000001 (NEEDED) Shared library: [android.hardware.graphics.allocator@3.0.so]
0x00000001 (NEEDED) Shared library: [libbinder.so]
0x00000001 (NEEDED) Shared library: [libcutils.so]
0x00000001 (NEEDED) Shared library: [libdisplayservicehidl.so]
0x00000001 (NEEDED) Shared library: [libhidlbase.so]
0x00000001 (NEEDED) Shared library: [libinput.so]
0x00000001 (NEEDED) Shared library: [liblayers_proto.so]
0x00000001 (NEEDED) Shared library: [liblog.so]
0x00000001 (NEEDED) Shared library: [libprocessgroup.so]
0x00000001 (NEEDED) Shared library: [libsync.so]
0x00000001 (NEEDED) Shared library: [libutils.so]
0x00000001 (NEEDED) Shared library: [libsurfaceflinger.so]
0x00000001 (NEEDED) Shared library: [libSurfaceFlingerProp.so]
0x00000001 (NEEDED) Shared library: [libc++.so]
0x00000001 (NEEDED) Shared library: [libc.so]
0x00000001 (NEEDED) Shared library: [libm.so]
0x00000001 (NEEDED) Shared library: [libdl.so]

Either there is a misconfiguration on my device tree or some things have changed with Android 11. I see that system boots to setup screen from adb logs but no display. Let's find what causes this. (kernel, hwcomposer,gralloc, exynos libraries or something else)