The company is based in Switzerland and is French speaking. Any chance "AdVite" means something different in French?

Apart from that, their website states pretty clearly their privacy policy [1] and other terms [2]. It doesn't look like there is anything shady going on here.

I don't personally use Migadu but I've had it bookmarked as the "service I would probably use if/when the day comes".

[1]: https://www.migadu.com/en/privacy.html [2]: https://www.migadu.com/en/terms.html