With LayoutNGPrinting shipped, we finally have full LayoutNG support everywhere. This also includes support for break avoidance between siblings. We've had support for the modern fragmentainer break controlling properties break-after, break-before and break-inside for some years already (in addition to the old page-break-before, page-break-after and page-break-inside properties). However, without LayoutNG, Blink didn't support the 'avoid' value on the break-before and break-after properties. This is supported in LayoutNG block fragmentation.