update: found the solution myself. After I additionally installed the MiHome App the Lightstrip immediately got detected and reinstalled propperly. So the problem was the Yeelight App - which btw now is detecting the Lightstrip again, too - after MiHome detected and reinstalled it.
Maybe there is device discovery cache at the beginning, pls don’t worry about it. BTW, if you select the same locale from Yeelight with mihome, you can also control the light strip from Yeelight.