Took a peek at the models they use. It seems to be a vision transformer encoder decoder architecture with a resent backbone. Looks really good. I had a similar idea of training a model and making a desktop application, but haven't had the opportunity. I wonder how much compute it took to train the model.

I think this paper was the first one to do OCR on LaTeX: http://cs231n.stanford.edu/reports/2017/pdfs/815.pdf The paper describes an Encoder-Decoder architecture with CNN encoder and LSTM based decoder.