Gajim [1] implements a lot of modern XEPs (directly or through easy to install plugins), including OMEMO. I don't know how well it works on non Linux systems (they provide Windows binaries at least).
Conversations indeed is very decent.
Most of the "big names" who provide modern and contemporary desktop IM apps deliver on the 3 platforms (Linux, macOS, and Windows), and use mostly web "technologies" (sometimes "pure browser", and sometimes with electron-like desktop "packaging")... so as a consequence, it is very native, indeed, but it is a generally consistent and continuous UX (user experience) between mobile/tablet and desktop/laptop.