Firefox userContent.css to fix color issues in input fields with dark themes. Place this file in ~/.mozilla/firefox/$PROFILE.default/chrome/

userContent.css

input:not([type='checkbox']):not([type='radio']),
textarea,
select {
  border: 1px solid #ddd;
  background-color: white;
  border-radius: 2px;
  padding: 0.4rem;
  color: black;
  -moz-appearance: none !important;
}

input:focus,
select:focus,
textarea:focus {
    box-shadow: 0px 0px 0px 4px rgba(28,149,230,1);
}

button,
input[type="reset"],
input[type="button"],
input[type="submit"] {
  border: 2px solid #ccc;
  background-color: #ccc;
  border-radius: 2px;
  padding: 0.4rem 0.6rem;
  color: black;
  -moz-appearance: none !important;
}

button:hover,
input[type="reset"]:hover,
input[type="button"]:hover,
input[type="submit"]:hover {
  filter: brightness(85%);
}

input[type="reset"]:focus,
input[type="button"]:focus,
input[type="submit"]:focus,
button:focus {
    box-shadow: 0px 0px 0px 4px rgba(28,149,230,1);
}

body {
  background-color: white;
  color: black;
  display: block;
  margin: 8px;
  -moz-appearance: none !important;
}

God bless you!! 👍