If I launch hyperion-dispmanx and watch log, it displays this
hyperion-dispmanx DISP : <INFO> Display opened with resolution: 4x1053481272
even if I input --width and --height as 100
maybe this can help. full log below
hyperion-dispmanx:
Version : 2.0.0-alpha.9 ((HEAD detached at 83338dc3) (Paulchen Panther-ca50487e/83338dc3-1605733041))
build time: Nov 18 2020 22:00:17
2021-04-08T04:13:12.813 hyperion-dispmanx DISP : <INFO> Display opened with resolution: 4x1053481272
2021-04-08T04:13:13.780 hyperion-dispmanx FLAT : <INFO> Connecting to Hyperion: My ip is listed here
2021-04-08T04:13:13.877 hyperion-dispmanx DISP : <ERROR> Snapshot failed: -1
2021-04-08T04:13:13.877 hyperion-dispmanx FLAT : <INFO> Connected to Hyperion: my ip is listed here
2021-04-08T04:13:13.971 hyperion-dispmanx DISP : <ERROR> Snapshot failed: -1
2021-04-08T04:13:34.062 hyperion-dispmanx DISP : <ERROR> Previous line repeats 200 times
2021-04-08T04:13:54.162 hyperion-dispmanx DISP : <ERROR> Previous line repeats 200 times
edit: This specific log is on libreelec, which admittedly is really hard to get dtoverlay and frambuffer settings to work