I'm gonna assume you're running this on wayland. Some unity games(under wine wayland) will have this kind of problem (no ui fonts). Try either running it with gamescope or with protonge. Though it's usually running this under gamescope(xorg/xwayland) that solves this.
edit: Don't forget to set up gamescope resolution and refresh rate settings.
edit: I've tested it and it works with with proton-ge. Both with and without gamescope. Both on xwayland and native wayland.