If you do not trust Tailscale as a company, here is an open source re-implementation of the server called headscale. Some/all clients are open source as well. So, you can review all components yourself or pay for a professional third-party review. Otherwise, if you take a binary blob from any origin, including Tailscale, and have it run with privileges on your server, there are few limits on what this blob can do. Yes, backdoors are technically possible, but probably bad for Tailscale’s business if that ever came to light.
Germany’s government is a three-party coalition where all three parties have lost in recent regional elections, so they try to show their profile ahead of the national election next year. Especially the party which now causes the most trouble (by appeasing an opposition party in a bid for a future coalition) got close to 0% of the vote in those regional elections. The chancellor himself has an unresolved history of being involved in a large tax evasion scheme (“cum-ex”) back when he was head of a regional government. Otherwise, he tries to do nothing wrong by not doing anything at all (ok, he does the day-to-day business, but no inspiring long-term goals or other leadership things). In contrast, the vice chancellor (from the Green party) does a noticeable better job at explaining and motivating the government’s decisions. Unfortunately, even this party has people in leading positions where they should not be …