The mouse appears, but does not work during install, meaning a user must use the tab key and enter, which is not an ideal user experience (seeing something not working, and having to use a keyboard).
This is related to the keyboard-not-working issue, which is incredibly persistent. We tracked it down to the expat package in Debian, but there seem to be more components involved, making it hard to pin down the issue.
Also, the internet connection being flaky here at Debconf is a problem for rebuilding the debian-installer. I'll do some more tests when I can (new images already exists, but the bug isn't gone yet).
Okay, the initial Debian bug that KiBi fixed was not the one we had in PureOS, but the exact same bug is affecting Debian now.
This issue is highly unstable in when it shows, but is at least reproducible with the same configuration of packages. Cyril is trying for find the cause of the problem by bisecting with Debian snapshots, and I am more randomly poking it to maybe find the cause of this issue.