Feel like the (totally impractical) fediverse end-game would be for each individual to have their own activitypub service, and federation happening on a person-by-person basis. So you retain some control over anything you publish, and your history is yours to keep.
As others have said, changing UPS batteries is required maintenance, and I agree 18-24 months is the typical service life for even high-end UPSs. However, you may want to look into LiFePO4 based UPSs, which can handle many more charge-discharge cycles and often have 5-year warranties. More expensive and potentially not as recyclable as lead acid batteries, but maybe appropriate for your use case.
draw.io is a capable web-based flowcharting program. Source code is on github but I’ve never tried locally hosting.
Of the changes made last week to the license, this one stands out:
That is a weird carve-out, so I’d guess the license revision (and technically the reason it’s no longer open source) somehow has to do with Atlassian or their plugin marketplace?