After seeing the Hydroxide app on OpenRepos.net for Sailfish OS, I was inspired to port it to Ubuntu Touch. A few crazy ideas later, and it's now a Rust app that runs the official Proton Mail Bridge instead of Hydroxide (alternative bridge).
So, this means you can now connect directly to Proton Mail with Dekko, or any other e-mail client you manage to get running on your UT device.
Find it in the Open Store: https://next.open-store.io/app/projectmoon.hydronium/
This thread will serve as a basic support/questions thing. For more detailed bug reports. please file an issue in the repository. I am particularly interested in any problems with the bridge itself, especially around the untested secondary mailbox password login.