Homelab To Do

Given what you've been building in your homelab (BookStack, Nginx Proxy Manager, Cloudflare, Proxmox), I'd strongly recommend Nextcloud Calendar.
My Recommendation: Nextcloud Calendar
Why it fits your use case:
✅ Self-hosted (LXC or Docker)
✅ Native CalDAV support
✅ Subscribe to external ICS feeds (AFL, F1, MotoGP, NRL, Premier League, etc.)
✅ Excellent mobile support (iPhone and Android)
✅ Multiple calendars with different colours
✅ Can be exposed through NPM/Cloudflare like your other services
✅ Easy to back up alongside your other containers
You can have:
Calendar
Source
Work
Synced from Exchange
AFL
ICS subscription
Formula 1
ICS subscription
Family
Manually maintained
Personal
Your own events
All displayed in a single calendar application.
Exchange → Nextcloud Sync
Since you already mentioned CalDavSynchronizer, the typical setup is:
Plain Text
Exchange Online
 ↓
CalDav Synchronizer
 ↓
Nextcloud Calendar (CalDAV)
 ↓
iPhone Calendar App
CalDav Synchronizer runs on your Windows PC and mirrors your Outlook calendar into Nextcloud.
Alternative solutions include:
Keeper.sh (open source) – supports Outlook, ICS and CalDAV sources. [github.com], [keeper.sh]
DAVMail – provides CalDAV connectivity for Exchange/O365. [sourceforge.net]
iPhone Access
On iOS you can simply add the Nextcloud account:
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Settings
→ Calendar
→ Accounts
→ Add Account
→ Other
→ Add CalDAV Account
Point it at:
Plain Text
https://calendar.yourdomain.com
(or whatever hostname you choose).
Your native Apple Calendar app will then show:
Work calendar
Sports calendars
Personal calendars
all together.
Best Sources for Sports ICS Feeds
A surprisingly good new project is:
Open Sports Cal – provides free ICS subscriptions for:
AFL
NBA
NHL
MLB
Formula 1
MotoGP
Premier League
World Cup
Many others. [github.com]
You simply subscribe using the ICS URL and Nextcloud refreshes automatically.
If You Want Something Lighter Than Nextcloud
Baïkal
Very lightweight:
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Baikal
 ├─ CalDAV
 ├─ CardDAV
 ├─ Tiny footprint
 └─ Easy LXC deployment
Excellent if you only need calendars and contacts.
The downside is that it's much more basic than Nextcloud.
What I Would Build In Your Homelab
For your current setup, I'd do:
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Proxmox LXC
 │
 ├── Nextcloud
 │ ├── Personal Calendar
 │ ├── Work Calendar
 │ ├── AFL Calendar
 │ ├── Formula 1 Calendar
 │ └── Family Calendar
 │
 ├── Nginx Proxy Manager
 └── Cloudflare
Then:
Plain Text
Outlook (work)
 ↓
CalDav Synchronizer
 ↓
Nextcloud
 ↓
iPhone Calendar
That gives you a single calendar app on your phone showing work, sporting events, and personal schedules all in one place with no Microsoft dependency beyond the Exchange source.