I heard you crying that the light theme is too bright. But I don't think so - here's a TRULY BRIGHT Discord theme (requires a HDR capable monitor).
Use any Discord theme loader (Vencord, BetterDiscord, Stylus in browser) to load the theme.
Open Settings, go to Appearance tab
Switch to Light theme (regular, not any of the Nitro ones)
Edit this value in flashbang.theme.css
:root {
/* Adjust brightness here */
--hdr-base-factor: 1;