Comment 11 for bug 1963751

> To upgrade to webkit2gtk 2.34.6-0ubuntu0.20.04.1, u-a must install libopengl0, either 1.3.1-1 from the main archive or 1.3.2-1~ubuntu0.20.04.1 from -updates. However, -updates is not a trusted source for u-a when configured like this, so the only candidate is 1.3.1-1. Unfortunately libopengl0 1.3.1-1 depends on libglvnd0=1.3.1-1, but 1.3.2-1~ubuntu0.20.04.1 is already installed, so u-a would have to downgrade it which is I guess a decision well beyond its pay-grade.

Oh, I believe this is the actually issue here. Unattended-upgrades only updates from the -security pocket, so a security update can't rely on something that is only in -updates.

I will look into pushing the binary packages from libglvnd to the -security pocket so that the upgrade can be handled properly.