[vorticalbox]

you can check the github https://github.com/cryptomator/ios

[delichon]

Even if I had the skills to confirm the code is secure, how could I know that this is the code running on my phone, without also having the skills to build and deploy it from source?

[warkdarrior]

Also, you need to make sure that the installation process does not insert a backdoor into the code you built from source.