Red Hat is moving to Jira (sadly) for RHEL. However we're still using BZ for Fedora and upstream projects, and likely will be for a very long time to come.

Do you know if it’ll still be publicly accessible? Browsing the BZ is usually how I gauged internal project timelines.

I certainly hope so.

Mozilla is using a mix of Bugzilla, Jira, Github Issues, and $DEITY knows what else, depending on the team or project in question. A good rule of thumb is that for any major system (code hosting, bug tracking, chat, wiki, CI, etc) Mozilla has at _least_ two- one homegrown and/or OSS, another a proprietary service- and a simmering battle over which should be used.

Most of Firefox engineering was still on their fork of Bugzilla (https://github.com/mozilla-bteam/bmo) when I left back in 2021.