12.3-RELEASE still uses Clang/libc++ 10 from 1 year ago. Do you plan to update in future as /stable/12 is supported until 2024-06-30?
libc++ lags behind libstdc++ on C++20 features and sticking to an old version puts the entire branch on a deathbed. Given drm-kmod on /stable/12 is stuck with Linux 4.16 era (discontinued after 2018-06-26) /stable/12 is already mostly dead from desktop POV. See also https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=215193 https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=260139
