This is theoretically completely safe, as long as you do everything correctly. This is open source, which significantly reduces the chances of bugs or hidden vulnerabilities that may have creaked into programming, and critical data like passwords are encrypted and stored locally on your device only.
However, your funds may still be at risk if you install wallets on a computer that is malware or connected to the Internet through insecure Wi-Fi networks. There is always some level of risk involved with internet connections.