Proton is working on a beta for Drive on Linux:
We are working towards releasing a beta of the official Proton Drive app for Linux. The initial launch will likely consist of our headless daemon mode only, meaning you’ll have a sync engine running that keeps a configurable list of directories up to date the same way it does on Mac and Windows.
cross posted from: https://programming.dev/post/58028970
Yes the app has been on the roadmap for years