These are the packages I've tested via a downgrade:
$ apt list --upgradeable Listing... Done libxcomposite1/focal 1:0.4.5-1 amd64 [upgradable from: 1:0.4.5-0ubuntu1] libxcomposite1/focal 1:0.4.5-1 i386 [upgradable from: 1:0.4.5-0ubuntu1] libxdamage1/focal 1:1.1.5-2 amd64 [upgradable from: 1:1.1.5-1] libxdamage1/focal 1:1.1.5-2 i386 [upgradable from: 1:1.1.5-1] libxfixes3/focal 1:5.0.3-2 amd64 [upgradable from: 1:5.0.3-1] libxfixes3/focal 1:5.0.3-2 i386 [upgradable from: 1:5.0.3-1] linux-generic/focal 5.4.0.25.31 amd64 [upgradable from: 5.4.0.21.25] linux-headers-generic/focal 5.4.0.25.31 amd64 [upgradable from: 5.4.0.21.25] linux-image-generic/focal 5.4.0.25.31 amd64 [upgradable from: 5.4.0.21.25] netplan.io/focal 0.99-0ubuntu1 amd64 [upgradable from: 0.98-0ubuntu4]
These are the packages I've tested via a downgrade:
$ apt list --upgradeable focal 1:0.4.5-1 amd64 [upgradable from: 1:0.4.5-0ubuntu1] focal 1:0.4.5-1 i386 [upgradable from: 1:0.4.5-0ubuntu1] generic/ focal 5.4.0.25.31 amd64 [upgradable from: 5.4.0.21.25] generic/ focal 5.4.0.25.31 amd64 [upgradable from: 5.4.0.21.25]
Listing... Done
libxcomposite1/
libxcomposite1/
libxdamage1/focal 1:1.1.5-2 amd64 [upgradable from: 1:1.1.5-1]
libxdamage1/focal 1:1.1.5-2 i386 [upgradable from: 1:1.1.5-1]
libxfixes3/focal 1:5.0.3-2 amd64 [upgradable from: 1:5.0.3-1]
libxfixes3/focal 1:5.0.3-2 i386 [upgradable from: 1:5.0.3-1]
linux-generic/focal 5.4.0.25.31 amd64 [upgradable from: 5.4.0.21.25]
linux-headers-
linux-image-
netplan.io/focal 0.99-0ubuntu1 amd64 [upgradable from: 0.98-0ubuntu4]