Rainloop web client used by Disroot and some others defaults to not showing images and needs you to click a button to display them. IIRC Protonmail is the same

Rainloop web client used by Disroot and some others defaults to not showing images and needs you to click a button to display them. IIRC Protonmail is the same in its webmail. The only non-web client I've used much in recent years is aerc, which is basically covered under "mutt" in this case.