Current users will have their install broken and need to google to figure out what is going on.
Future users will install `keepassxc` thinking it would be actually KeePassXC before potentially realizing its a minimal version.
Personally I think splitting it into `keepassxc-full` and `keepassc-minimal` would be better since it moves the choice to the user instead of implying the contents.
apt shows the NEWS file during update when there's a change. If it doesn't (ie. user set it up to blindly do the upgrade), you can still check the news file or .debian.changelog.gz file afterwards.
And note that this happened in testing/sid channel, where breakage is supposed to be happen. When this change shipped in the new major Debian stable release in a few years, it'll surely be clearly written in the release notes.
What else do you expect, SMS notification? :P
If a user haven't seen the above he for sure won't see an announcement in a crowded debian-whatever-announce mailing list he isn't subscribed to or an obscure blog post posted somewhere he doesn't follow.