I also miss the "BlackBerry Hub" feature, which would aggregate your emails, BlackBerry messenger messages, and SMS messages into a single UI. It even pulled in notifications from Android apps, though opening them switched to that app rather than letting you reply in-line.
I bought mine after they had already released Android compatibility for any APK you cared to load, but unfortunately I think that feature was too little, too late.
I've been on an iPhone SE since around 2016. If I had the option to go back to using the BB Classic hardware/OS as it was when I switched, but with third-party app support and security updates, I would do it without second thought.