Drop your restriction on “no smart home” stuff and you can do it.
See my post here for ideas: Ultimate LED Bulbs - Ultra High CRI - The Honorable Quest - #440 by contactcr
ZigBee is secure, long range, and local (does not need internet). You will need a compatible hub which you will need to determine what fits your needs.
Not all smart home stuff is created equal though so YMMV. Z-wave is also local, bluetooth is local (but mediocre at best), there are some wifi local ones but they are the minority and the specs on these knockoff brands that use wifi or remotes are questionable. Maybe Germany has a rating organization for things sold locally you can trust though like we do in the US.