The best you can do is to go for hardware wallet like Trezor.
Exodus can hold other crypto currencies apart from Bitcoin. I guess they are open source too ,you can look up their code on GitHub.
You can get the app from their official site
Exodus is a close source wallet.
OP, you can use unstoppable wallet as it is an open source wallet that can be used for bitcoin and other cryptocurrency.
Unstoppable wallet is open source but it is ao ile eallet and not having a Desktop version. OP is looking for a desktop wallet and all the ones that are know are close source except bitcoin wallets that we have many open source ones.