This is odd, it happened to me a while back where the text formatting and image buttons are all greyed out. It's fine now, and I can't remember if it was something I did or if it just fixed itself. Sorry, I realise this post adds little of value other than 'me too'.
FWIW I am using Samsung S21 Plus, and the Samsung browser. Android 13/OneUI 5.1 so fully updated. No issues with it at the moment. I don't know what caused it to happen, it just stopped working properly one day, and then was OK after a couple of weeks.