Dr. Daniel Brubaker has caused quite a stir with his book Corrections in Early Qurʾān Manuscripts: Twenty Examples and his YouTube channel, Variant Quran. The YouTube channel has been remarkable successful considoring that it has at the time of writing only 36 videos of which the majority were uploaded in the first two years. Dispite this low number of uploads, it has still managed to collect 26k subscribers and had 777k views. Brubaker on his channel comments;
Dr. Daniel Brubaker has carefully examined more than 10,000 pages of the earliest Quran manuscripts, most of them in person. His doctoral dissertation, "Intentional Changes in Qurʾān Manuscripts" (Rice University, 2014) has captured the interest of many and formed the foundation for further investigations. Driving Brubaker's inquiry is a curiosity about the early history of the Quran, and he is aware that the early manuscripts are witnesses to a time not easily accessed via other avenues of investigation. Brubaker launched this channel, "Variant Quran" in mid-2020 as an outlet for discussion of his work with corrections and variants in Quran manuscripts. He tries to upload informative videos discussing relevant research and analysis, interviews, and answers to viewer questions about once a week.
This what Gerd-R. Puin commented about his book;
“In Qur'anic research, the text has always been regarded as more or less comprehensible with the help of its Muslim exegetes. In a way, one could qualify the approach as one-dimensional, based on the latest interpretation of an ancient scripture. However, in recent years an increasing wave of Arabic Qur'an editions of different but equally valid Readings has been edited, opening a second dimension, a wide field of research opportunities on the range of scriptural and oral traditions which have led to those different Readings. In addition to these there is a growing activity in editing or presenting early manuscripts of the Qur’an, so that it is not an exaggeration to characterize this stadium as the third dimension of the Qur’an’s history. One of the few remaining pioneers in this domain is Dan Brubaker, who discovers the minute 'corrections’ on the old parchments, which he investigated in the main collections all over the world. He compares the corrections with the earlier versions underneath, and in his analyses of the different types of corrections he observes even the sensible and frequent "omission" of the word "Allah" in the lower text, or frequent corrections of "rizq" or the eschatological "sa'ah / hour" [...] Dan Brubaker’s approach is as modest as it is scientifically sound [...]. In addition [...], he has found a way to lead the reader through a highly sophisticated topic, so that familiarity with Arabic is not even necessary to follow his arguments.” -- Gerd-R. Puin, Universität des Saarlandes (retired)"

Dr Daniel Wallace commented;
“It has long been popularly asserted that, in contrast to that of the New Testament, for example, the Qur’an’s manuscript tradition is pristine and perfect, without ever a mark out of place, much less a variation involving whole words or phrases. Brubaker’s fascinating study demonstrates that this is not quite so. What the author has done in this short book is to distill years of research, making accessible to a general readership significant and interesting examples of scribal corrections in some of the earliest Qur’an manuscripts. This book about corrections in handwritten copies of the Qur’an offers its own correction of a widespread but faulty view about the Qur’an.” -- Daniel B. Wallace, Executive Director, Center for the Study of New Testament Manuscripts
Brubaker has surveyed some 10,000 pages of early Quran manuscripts, documenting post-production physical corrections. To date, he has noted and described thousands, with various causes including (but not limited to) simple scribal error. Brubaker is working on several academic books, but has found the subject is also of interest to non-academic readers. "Corrections in Early Qurʾān Twenty Examples" is an introduction to the range of the phenomenon, written to be accessible to non-specialists. In it, he selects a group of corrections from a variety of early Quran manuscripts of this early period. For each example, he shows a picture and gives a brief description, followed by a diagram showing the correction in relation to a modern standard edition of the Quran.
Dr Brubaker's book has stirred up a storm in both the Christian world and the Islamic world. Many Islamic scholars and apologists have jumped up to "correct" him. Those jumping up has included people like Yasir Qadhi, Tayyar Altikulaç, Hythem Sidky and Dr Shabir Ally, to name just a few.
Dr Brubaker's response has been, what is there to correct - it is just photographs of the manuscripts.
I think the important point to make is, that we are not saying that the Quran should not have variance in it and scribal errors. All ancient documents that are copied by hand have such errors. The point is that the standard Islamic narrative is that the Quran that we have today is exactly the same the same as the one delivered to Muhammad. The plain fact is that, that narrative is wrong. Islam has to face up to that fact and stop repeating that narrative parrot fashion - it is something I hear or read or the time. Once that is accepted, we can get down to discussing what the Quran and Islam actually teaches.