Merkuro looks so good! The previous calendar was unusable for me, but good KDE Software is really nice.
I wish the Akonadi stuff could run as a Flatpak runtime though, to support multiplatform. But I am not sure if this requires IPC or also native messaging.
Kontact is on Flathub, so it is definitely possible.
EDIT: Merkuro is apparently bundled with the Kontact Flatpak. Seems like they're just shoving anything that uses Akonadi in that package. So on one hand, it seems there is a Merkuro Flatpak already. On the other hand, it's bundled with a bunch of extra stuff you probably don't need if you're using Merkuro (like the entire Kontact suite), so you're probably better off with distro packages.
Oh ripping cds was my last use case for k3b :(
I'll check out Audex but why does it specifically say CD-ROM multiple times on the site? https://apps.kde.org/de/audex/
Is it not for regular, pressed audio cds? (CDDA) Why would I need it for a CD-ROM?