Some ideas:

• Use background-blend-mode somehow, see T358513#9578928 and https://gerrit.wikimedia.org/r/1006946 for an initial exploration
• Change the markup of the CSS-only Select component to something like <div class="cdx-select"><select> ... </select></div>, so that we can then use :after for the icon (or add a separate <span> for the icon). Avoid a breaking change by writing the styles such that they still work for the old markup, but without night mode support.

Change 1007462 had a related patch set uploaded (by Catrope; author: Catrope):

[design/codex@main] [Proof of concept] Select: Make CSS-only icon work in dark mode

https://gerrit.wikimedia.org/r/1007462

This introduces a second hack into the Select component code related to supporting CSS custom properties - should we capture the work to create a more sustainable solution in the future somewhere?

cc @CCiufo-WMF ^

Do we have ideas about what a more sustainable solution might be, or would the follow up work be a spike to investigate further?

@CCiufo-WMF the latter; we've thrown around some ideas but are far from a solid long-term solution IMO

Ok, thanks! I'd suggest we create a future spike in the backlog to revisit this. @AnneT or @Catrope could one of you create the task with the context of why the approaches taken so far are hacks?