Thanks for the answeer, the settings you suggested were already configured. However maybe I've found something. Looking at the differences between the good log and the bad one, the problem seems to start after:
2022-01-31 12:57:49.389 T:887 DEBUG <general>: CWinSystemGbm::InitWindowSystem - initialized DRM
2022-01-31 12:57:49.389 T:887 WARNING <general>: CWinSystemGbm::UpdateResolutions - Failed to get resolutions
I tried configuring config.txt with the lines:
hdmi_group=1
hdmi_mode=16
and the first tests are positive.