It is stupid to store anything in closed source wallets since you have no idea what is happening in the background. The best case scenario is that they aren't malicious and you lose your funds due to a bug and worst case scenario is that they are malicious and not only they are monitoring everything you do but also they have all your private keys.

Ownr is completely closed source
Lumi has some libraries on Github but not a proper source code and it is not popular at all