I have a LattePanda 3 Delta running Debian. It does not see the display that is connected to the HDMI port, so it runs only in 800x600 resolution. When the display is connected to a Raspberry Pi, the Pi runs at full resolution.

xrandr --verbose on the 3 Delta reports:

Screen 0: minimum 800 x 600, current 800 x 600, maximum 800 x 600
default connected 800x600+0+0 (0x520) normal (normal) 0mm x 0mm
Identifier: 0x51f
Timestamp: 46270
Subpixel: unknown
Clones:
CRTC: 0
CRTCs: 0
Transform: 1.000000 0.000000 0.000000
0.000000 1.000000 0.000000
0.000000 0.000000 1.000000
filter:
non-desktop: 0
supported: 0, 1
800x600 (0x520) 36.000MHz *current
h: width 800 start 0 end 0 total 800 skew 0 clock 45.00KHz
v: height 600 start 0 end 0 total 600 clock 75.00Hz

xrandr --verbose with the same monitor on the Raspberry Pi reports:

Screen 0: minimum 320 x 200, current 1920 x 1080, maximum 7680 x 7680
HDMI-1 connected primary 1920x1080+0+0 (0x48) normal (normal left inverted right x axis y axis) 477mm x 268mm
Identifier: 0x45
Timestamp: 26061
Subpixel: unknown
Gamma: 1.0:1.0:1.0
Brightness: 1.0
Clones:
CRTC: 0
CRTCs: 0
Transform: 1.000000 0.000000 0.000000
0.000000 1.000000 0.000000
0.000000 0.000000 1.000000
filter:
EDID:
00ffffffffffff0010ac65a053543431
2615010380301b78ea81f5a357539f27
0a5054a54b00714f8180d1c001010101
010101010101023a801871382d40582c
4500dd0c1100001e000000ff00595059
344e31394b313454530a000000fc0044
454c4c205354323232304c0a000000fd
00384c1e5311000a2020202020200163
02031ff14c9005040302071601141f12
132309070765030c0010008301000002
3a801871382d40582c4500dd0c110000
1e011d8018711c1620582c2500dd0c11
00009e011d007251d01e206e285500dd
0c1100001e8c0ad08a20e02d10103e96
00dd0c11000018000000000000000000
000000000000000000000000000000af
Output format: Automatic
supported: Automatic, RGB, YCbCr 4:2:2, YCbCr 4:4:4
Broadcast RGB: Automatic
supported: Automatic, Full, Limited 16:235
max bpc: 8
range: (8, 12)
bottom margin: 0
range: (0, 100)
top margin: 0
range: (0, 100)
right margin: 0
range: (0, 100)
left margin: 0
range: (0, 100)
Colorspace: Default
supported: Default, SMPTE_170M_YCC, BT709_YCC, XVYCC_601, XVYCC_709, SYCC_601, opYCC_601, opRGB, BT2020_CYCC, BT2020_RGB, BT2020_YCC, DCI-P3_RGB_D65, DCI-P3_RGB_Theater
link-status: Good
supported: Good, Bad
CONNECTOR_ID: 32
supported: 32
non-desktop: 0
range: (0, 1)
1920x1080 (0x48) 148.500MHz +HSync +VSync *current +preferred
h: width 1920 start 2008 end 2052 total 2200 skew 0 clock 67.50KHz
v: height 1080 start 1084 end 1089 total 1125 clock 60.00Hz
1920x1080 (0x49) 148.500MHz +HSync +VSync
h: width 1920 start 2448 end 2492 total 2640 skew 0 clock 56.25KHz
v: height 1080 start 1084 end 1089 total 1125 clock 50.00Hz
1920x1080 (0x4a) 148.352MHz +HSync +VSync
h: width 1920 start 2008 end 2052 total 2200 skew 0 clock 67.43KHz
v: height 1080 start 1084 end 1089 total 1125 clock 59.94Hz
1920x1080i (0x4b) 74.250MHz +HSync +VSync Interlace
h: width 1920 start 2008 end 2052 total 2200 skew 0 clock 33.75KHz
v: height 1080 start 1084 end 1094 total 1125 clock 60.00Hz
1920x1080i (0x4c) 74.250MHz +HSync +VSync Interlace
h: width 1920 start 2448 end 2492 total 2640 skew 0 clock 28.12KHz
v: height 1080 start 1084 end 1094 total 1125 clock 50.00Hz
1920x1080i (0x4d) 74.176MHz +HSync +VSync Interlace
h: width 1920 start 2008 end 2052 total 2200 skew 0 clock 33.72KHz
v: height 1080 start 1084 end 1094 total 1125 clock 59.94Hz
1280x1024 (0x4e) 135.000MHz +HSync +VSync
h: width 1280 start 1296 end 1440 total 1688 skew 0 clock 79.98KHz
v: height 1024 start 1025 end 1028 total 1066 clock 75.02Hz
1280x1024 (0x4f) 108.000MHz +HSync +VSync
h: width 1280 start 1328 end 1440 total 1688 skew 0 clock 63.98KHz
v: height 1024 start 1025 end 1028 total 1066 clock 60.02Hz
1152x864 (0x50) 108.000MHz +HSync +VSync
h: width 1152 start 1216 end 1344 total 1600 skew 0 clock 67.50KHz
v: height 864 start 865 end 868 total 900 clock 75.00Hz
1280x720 (0x51) 74.250MHz +HSync +VSync
h: width 1280 start 1390 end 1430 total 1650 skew 0 clock 45.00KHz
v: height 720 start 725 end 730 total 750 clock 60.00Hz
1280x720 (0x52) 74.250MHz +HSync +VSync
h: width 1280 start 1720 end 1760 total 1980 skew 0 clock 37.50KHz
v: height 720 start 725 end 730 total 750 clock 50.00Hz
1280x720 (0x53) 74.176MHz +HSync +VSync
h: width 1280 start 1390 end 1430 total 1650 skew 0 clock 44.96KHz
v: height 720 start 725 end 730 total 750 clock 59.94Hz
1024x768 (0x54) 78.750MHz +HSync +VSync
h: width 1024 start 1040 end 1136 total 1312 skew 0 clock 60.02KHz
v: height 768 start 769 end 772 total 800 clock 75.03Hz
1024x768 (0x55) 65.000MHz -HSync -VSync
h: width 1024 start 1048 end 1184 total 1344 skew 0 clock 48.36KHz
v: height 768 start 771 end 777 total 806 clock 60.00Hz
800x600 (0x56) 49.500MHz +HSync +VSync
h: width 800 start 816 end 896 total 1056 skew 0 clock 46.88KHz
v: height 600 start 601 end 604 total 625 clock 75.00Hz
800x600 (0x57) 40.000MHz +HSync +VSync
h: width 800 start 840 end 968 total 1056 skew 0 clock 37.88KHz
v: height 600 start 601 end 605 total 628 clock 60.32Hz
720x576 (0x58) 27.000MHz -HSync -VSync
h: width 720 start 732 end 796 total 864 skew 0 clock 31.25KHz
v: height 576 start 581 end 586 total 625 clock 50.00Hz
720x576i (0x59) 13.500MHz -HSync -VSync Interlace
h: width 720 start 732 end 795 total 864 skew 0 clock 15.62KHz
v: height 576 start 580 end 586 total 625 clock 50.00Hz
720x480 (0x5a) 27.027MHz -HSync -VSync
h: width 720 start 736 end 798 total 858 skew 0 clock 31.50KHz
v: height 480 start 489 end 495 total 525 clock 60.00Hz
720x480 (0x5b) 27.000MHz -HSync -VSync
h: width 720 start 736 end 798 total 858 skew 0 clock 31.47KHz
v: height 480 start 489 end 495 total 525 clock 59.94Hz
720x480i (0x5c) 13.514MHz -HSync -VSync Interlace
h: width 720 start 739 end 801 total 858 skew 0 clock 15.75KHz
v: height 480 start 488 end 494 total 525 clock 60.00Hz
720x480i (0x5d) 13.500MHz -HSync -VSync Interlace
h: width 720 start 739 end 801 total 858 skew 0 clock 15.73KHz
v: height 480 start 488 end 494 total 525 clock 59.94Hz
640x480 (0x5e) 31.500MHz -HSync -VSync
h: width 640 start 656 end 720 total 840 skew 0 clock 37.50KHz
v: height 480 start 481 end 484 total 500 clock 75.00Hz
640x480 (0x5f) 25.200MHz -HSync -VSync
h: width 640 start 656 end 752 total 800 skew 0 clock 31.50KHz
v: height 480 start 490 end 492 total 525 clock 60.00Hz
640x480 (0x60) 25.175MHz -HSync -VSync
h: width 640 start 656 end 752 total 800 skew 0 clock 31.47KHz
v: height 480 start 490 end 492 total 525 clock 59.94Hz
720x400 (0x61) 28.320MHz -HSync +VSync
h: width 720 start 738 end 846 total 900 skew 0 clock 31.47KHz
v: height 400 start 412 end 414 total 449 clock 70.08Hz
HDMI-2 disconnected (normal left inverted right x axis y axis)
Identifier: 0x46
Timestamp: 26061
Subpixel: unknown
Clones:
CRTCs: 4
Transform: 1.000000 0.000000 0.000000
0.000000 1.000000 0.000000
0.000000 0.000000 1.000000
filter:
Output format: Automatic
supported: Automatic, RGB, YCbCr 4:2:2, YCbCr 4:4:4
Broadcast RGB: Automatic
supported: Automatic, Full, Limited 16:235
max bpc: 8
range: (8, 12)
bottom margin: 0
range: (0, 100)
top margin: 0
range: (0, 100)
right margin: 0
range: (0, 100)
left margin: 0
range: (0, 100)
Colorspace: Default
supported: Default, SMPTE_170M_YCC, BT709_YCC, XVYCC_601, XVYCC_709, SYCC_601, opYCC_601, opRGB, BT2020_CYCC, BT2020_RGB, BT2020_YCC, DCI-P3_RGB_D65, DCI-P3_RGB_Theater
link-status: Good
supported: Good, Bad
CONNECTOR_ID: 42
supported: 42
non-desktop: 0
range: (0, 1)

What should I do to get the LattePanda to recognize the monitor?