Many cloud storage providers require your full trust that they will not look at your files. The alternatives listed below eliminate the need for trust by either putting you in control of your data or by implementing E2EE.
If these alternatives do not fit your needs, we suggest you look into Encryption Software.
Cryptee is a web-based, encrypted, secure photo storage service and documents editor.
Nextcloud is a suite of free and open-source client-server software for creating your own file hosting services on a private server you control. It also comes with experimental E2EE.
We recommend checking if your Nextcloud provider supports E2EE, otherwise you have to trust the provider to not look at your files.
When self-hosting, you should also enable E2EE to protect against your hosting provider snooping on your data.
Proton Drive is an E2EE general file storage service by the popular encrypted email provider Proton Mail.
Proton Drive is currently in beta and is only available through a web client and an Android app.