7-zip is open source so you can securely download the source, inspect it yourself, compile the source, and be on your way.
Alternatively, you can use WSL to give yourself a reproducible Linux environment in Win10 where you can download a 7zip extractor securely, and extract Dolphin that way.
Alternatively, you can use WSL to give yourself a reproducible Linux environment in Win10 where you can download a 7zip extractor securely, and extract Dolphin that way.