Somewhat belatedly given the last update was in xcb-proto 1.13 in 2017...
Quoting @smcv from https://bugs.debian.org/921069:
libxcb-dri3 version 1.13 appears to have added new symbols without increasing the minor ABI version in its -version-info. This will break anything that compares libraries by their version info to decide which one is newer.
The Steam Runtime uses libraries' major/minor/micro ABI version info (in this case 0.0.0) to decide whether to use the system copy of a library or the copy in the Steam Runtime, depending on which one is newer (#921026). We can work around this by adding a versioned dependency on libxcb-dri3-0 and deleting the copy from the Steam Runtime, but this isn't a particularly scalable solution.