Yep, Germany in general has a pretty active open source community, so there are already a lot of alternatives out there. Unfortunately, most IT people are bad at marketing, which is why hardly anyone knows about these alternatives.

Their official server in the fediverse (https://social.bund.de/public/local) with currently 99 active government agencies and institutions.

I bought a Portable Power Station (e.g. Anker SOLIX C300) to use as an Uninterruptible Power Supply (UPS) for my homeserver (~ 40 Watt) to buy me - or better my utility company - a few hours in case the power fails.