I looked into shared calendars a few years ago, and looked at pretty much every option there was. Crucially, we needed something platform-agnostic as we’ve a mix of PCs, iDevices, Androids and a Windows phone, as well as Enterprise concerns (Exchange and the corporate Google offering). Google Calendar turned out to be the glue that held everything together.
So, now my Google account has two calendars (plus the other gubbins that you tend to accrue like “UK Holidays”); my personal calendar and a Shared calendar. My personal one is largely work stuff, and syncs to Google from Exchange with a third party app called gSyncit. My OH has full access to the Shared calendar, granted to her own Gmail a/c. everything else Just Works, obviously it’s natively supported in Android and likewise it auto-syncs from my OH’s Apple things (though I’m not sure offhand how that was set up). For us, it’s perfect.
What I don’t have is a satisfactory shared notes system. I’ve tried loads and they all have their own quirks, weird sync issues and the like, though it’s a while since I last looked at it so am probably due a revisit. Open to suggestions.
Haven’t heard of ‘hubapp’, will take a look. Ta.