Weird I thought this was fixed already in the normal Steam client (issue is one month old, fixed since then in the Steam beta client back then, to this day).
//EDIT: yep, last month issue [Testing Update] 2021-09-02 - Kernels, Systemd, Wine, Deepin, KDE Gear, Maui-Kit, Plasma - #18 by stephane
//EDIT2: and in the known issues there too [Stable Update] 2021-09-04 - Kernels, Wine, Deepin, KDE Gear, Maui-Kit, Plasma - #3 by philm
Weird you just got the issue now.
I switched to the beta last month and since then no issue, to this day.
Here is the Steam issue Built-in browser incompatible with freetype2 2.11.0 · Issue #7935 · ValveSoftware/steam-for-linux · GitHub