All browsers support CSP's request-uri, but Firefox doesn't support the Reporting API which report-to depends on. It's been behind a flag for years, and now isn't even available behind a flag because the implementation is outdated (https://bugzilla.mozilla.org/show_bug.cgi?id=1775194).
I've disabled CSP reporting for regular users via https://gitlab.com/composr-foundation/composr/-/commit/65ec77311484d4404d1c9b143f6dbec2eac3fabc so to avoid console errors.
So makes sense to hold off on this.