Just adding a small update after a bit more testing on my side (still Suzie here).

I realized that what I really need isn’t a full modern calendar interface running locally, since my Pentium III clearly struggles with anything web-heavy, but rather a lightweight bridge that synchronizes calendars before they reach the machine. The goal is simply to propagate busy/free slots across services so the old workstation only has to read one simple calendar feed.

While searching for alternatives to manual .ics exports, I came across a service that focuses exactly on this idea : syncthemcalendars.com. From what I understand, it can sync multiple calendars together so availability is mirrored automatically without needing a modern browser constantly logged into Google or Outlook.

I haven’t fully stress-tested it yet, but conceptually it seems closer to what older hardware needs: let a remote service handle synchronization, then subscribe locally to a single lightweight calendar. That should reduce CPU load and avoid freezes caused by current web apps.

If anyone else is running legacy machines as utility workstations, I’d be curious to know what synchronization setups you’re using, especially solutions that don’t require heavy JavaScript or recent TLS stacks.