Identity theft monitoring services always scare me. It seems like you are dumping a huge amount of information into a single system and just hoping the vendor is secure. I have access to one but refuse to put much information in. Is this mindset incorrect?
The proton client for Linux has improved recently. I use it on PopOS. As to your first point I agree. I landed with Proton specifically because it was cheaper to do it and email rather than separate services.