Is it really always an intellectual doubt? Things like moral/ethical 'doubts' are fully obliterated with even a basic understanding of moral philosophy. The basic principle being whatever is Divinely revlealed(theoretically) reaches a level of objectivity and everything else would not even challenge the crown of objectivity. Evolution? Learn about the emprical method and its limitations and range of operation as well as the thought experiment of different narratives(not sure of the name). Scientific critique, falls in the same category. It usually does not matter much. At the end of the day one could still doubt and redoubt. The actual issue with 'linked' person seems to be that she came from a salafi version of islam without any spiritual and inner sweetness. A creed which contradicts sound reason. A condemnation of spiritual growth, by prohibiting tested methods of our ancient masters and awliya. The simple term for that person is a 'Salafi Burnout'. There's a heavy emphasis on outward religiousity but the simple 'spiritual' experiences are ignored. Certainty/yaqin is achieved only through inner unveilings. Was that not one of the main points of Al-Ghazalis al munqidh min ad dalal? The soothness of the heart from reciting Quran and unexplained tears upon hearing and reciting it, doing dhikrullah with prayer beads(something we know salafis reject), reciting mawlid and lots of salawat, dalailul khayrat? Things like that get rid of doubt much more effectively than trying to refute every single 'psuedo-intellectual' doubt. There is an answer to all of them but it is a regressing spiral and a waste of resources. Instead the mentality of the person becomes like this, 'I already know that this is true with certainty but I have not acquired enough knowledge to respond/grasp/refute such and such' .
wiki page worth reading for western Muslim parents, Islamic teachers, and educationists teaching secular education - to come up with strategies, q&A's, course content, responses to doubts etc. for Muslim kids and youth - in order to prevent apostasy we can't take our weekly durus, Sunday schools, and Islamic schools (secular ed or darse Nizami based) for granted when it comes to safeguarding kids faiths https://en.m.wikipedia.org/wiki/Aliyah_Saleem
