I've been testing out the rclone Proton Drive integration for a bit. As it is today, the rclone approach is currently too slow, especially using the "mount" approach which lets you access Drive files on-the-fly only downloading data as needed.
Using an "sync" approach (where data is stored both locally and in Drive) might be a better approach, unless you expect rapid syncing of files.
Considering the setup efforts, I cannot recommend Proton Drive for Linux in a productivity context.
Alternatives to Proton Drive on Linux there is @filen and Tresorit, which are both fully #e2ee. I've been using both for a while and both are decent.
Filen is the cheapest alternative and feature wise pretty close to Proton Drive - but they have a sync client for Linux. They do not have a possibility to access files "on-the-fly"; all data must be synced locally. And sharing data via URL need to happen via the web portal. Sharing data between Filen users was read-only access last time I checked.
Tresorit is fairly expensive, but also a lot more feature rich, especially on the sharing side. The Linux client supports both synchronising files between local storage and the cloud as well as a "drive mount" where all files in the cloud are available and only downloaded once you access it - or uploaded directly if you store something there.
Both Filen and Tresorit are fairly efficient in regards to uploading and downloading data via their sync clients. Using the web portal is slower, especially on larger files. This is naturally and not unexpected; the data is decrypted first on your device when the data has been downloaded from the cloud storage. Proton Drive is no different here.
Filen is a more properly open source based product. Tresorit is non-open source and built on top of Microsoft Azure services.