Explanation: Lock Xpra packages to v6.4
Package: xpra*
Pin: version 6.4*
Pin-Priority: 1000

Explanation: xpra-html5 uses different version scheme, lock it to v19
Package: xpra-html5
Pin: version 19*
Pin-Priority: 1000

Explanation: Block the installation of other xpra versions
Package: xpra*
Pin: version *
Pin-Priority: -1