Ooh. I have used Soulver on iOS for nearly a decade now. Sadly, the developer has pulled it from the App Store for a long time, so I can’t point others to it. For me, Soulver has the ideal UI for a phone screen. The one thing I really feel it is missing is a cross-platform sync. I used the iCloud integration and Mac app, but if I could access my worksheets from Linux and Windows just as easily I would be totally happ…
Have you tried Calca? https://calca.io/
It works really great on mobile too (even their website is not updated it works fine on latest OSs).