SUMMARY
I was trying to add a Moodle calendar to KOrganizer, which gives you a calendar URL in VCALENDAR format. After adding it as an "iCal Calendar File" via the URL, it creates an empty calendar called "akonadi_ical_resource_n" (where n is a number). Neither syncing the calendar nor restarting KOrganizer nor restarting Akonadi populates it.

I tried messing around with it in Akonadi Console and found that restarting the ical agent for the calendar makes it sort of work: it creates another calendar with the actual name I gave it in the add dialog which has all the entries in it, but the old "akonadi_ical_resource_n" one stays and trying to remove it to clean it up because it's useless takes the actual calendar with it, probably because they are owned by the same agent. (I ended up clearing out all the content types in the Internals tab, yes, the one that says "Do not even think about changing anything in here!" ;), to make it at least not show up anymore.)

STEPS TO REPRODUCE
1. Add a VCALENDAR URL via the iCal type, optionally give it a name
2. The added calendar doesn't have the name you input and it doesn't sync either
3. Restart the agent in Akonadi Console to have the actual calendar show up but the empty one stay

OBSERVED RESULT
The added calendar ignores the name you gave it and never gets populated.

EXPECTED RESULT
The added calendar populates with the data behind the URL.

SOFTWARE/OS VERSIONS
Operating System: Gentoo 2.8
KDE Plasma Version: 5.23.80
KDE Frameworks Version: 5.88.0
Qt Version: 5.15.2
Kernel Version: 5.14.14-gentoo-dist (64-bit)
Graphics Platform: Wayland
Processors: 12 × AMD Ryzen 5 5600X 6-Core Processor
Memory: 23.4 GiB of RAM
Graphics Processor: Radeon RX Vega

ADDITIONAL INFORMATION
KOrganizer commit 7ab02ec
Akonadi commit 21dc82c