I’m experiencing a similar issue that started today.
Dark Theme + Primary color: #ecff00 (neon-yellow)
Before when using style “Accented footer”, menu text/icons were rendered dark.
Since today, text/icons display in white in the very same, yet existing App (in contrast to the situation of the OP).
Same is true for Action button icons with Prominence “Display overlay”.
One hardly can read/see the text/icon.
Switching to style “colored”, menu text/icons correctly switch back to a dark grey (inactive tab) and black (active tab), but the icon on action buttons are still white.
Furthermore, I realise that calendars forth and back arrow icons (used to switch weeks) remain black when dark theme is chosen. One can hardly spot them.
Dark theme with accented Footer style
Dark theme with colored style
What can I do about it?