Yeah, unfortunately, the seeed does not use ili9881c from the “vanilla” kernel but uses own ili9881d (which kind of makes sense since the latter is different resolution). It feels like it should be possible to upstream ili9881d driver but that’s another discussion 
What i’ve noticed is that with kernel 5.15 drm/vc4 logs the following:
[ 6.825544] [drm] Initialized vc4 0.0.0 20140616 for gpu on minor 1
and 5.10 logs the following:
[ 6.496895] [drm] Initialized vc4 0.0.0 20140616 for gpu on minor 0
Is it DSI0 vs. DSI1 issue? Is it caused by a mistake in the custom mipi_dsi module, or is it something addressable as an overlay? 