Hello,
Actually, I had this problem since I installed Windows in English language with Spanish keyboard, but I just found out the way right now. You have to ensure you have only one keyboard layout installed. Windows shows the switcher if there is more than one layout, even under a single language.
Open Settings > Time and language > Language and region > Click your language > Language options, and under Keyboards remove every layout except the one you actually use. With only one layout present, the switcher no longer appears.
Let me know if this works!