Yeah, I tried tuta. I have (overall less but) the same issue with proton. I just want to use my own client apps of choice.
I have registered with mailbox.org and while the trial period is very limited, the web ui is minimalistic and basic looking. You could say outdated. I seriously consider paying for a "team" account for me and my wife. The price is unbeatable. Aside from the gui, the features I need are there.
I just need the Wife's approval. She'd be migrating from yahoo of all places.
When will they learn that architecture change is a game of software support and getting devs on board for it. The last launch was a dumpsterfire precisely because of this.
You can brute force x86 emulation with more cores and more gigahertz. But why use an arm cpu at that point? Modern x86 mobile chips also came a long way in terms of power and efficiency. A quad core desktop cpu from 2013 is enough for casual computing still.