I really like typesetting with unicode math symbols. I use them in my notes, sometimes even in LaTeX as we get the unicode-math package. To input unicode symbols in Emacs I use the unicode-math package and before that my own-grown input method. The input method is bound to a buffer so when you switch (intentionally or not) to another buffer typing \alpha will not result in a pretty α being rendered. I can live with this. Except when switching to the minibuffer!

The minibuffer better be aware of my current input method! So be it!

(defun minibuffer-input-method-initialize ()
  "Initialize input method from `minibuffer-selected-window'."
  (let* ((win (minibuffer-selected-window))
         (buf (and win (window-buffer win))))
    (when buf
      (activate-input-method (buffer-local-value 'current-input-method buf)))))

 (use-package emacs
   :ensure nil
   ...
   :hook ((minibuffer-setup-hook . minibuffer-input-method-initialize)))