Plant-based proteins have been promoted in research for various reasons. First, more people choose to live sustainably with environmental concerns. Moreover, adequate proteins are required for the new challenge in an expanding world population. Furthermore, from an industrial perspective, extracting nutrients from cheaper sources with better value in both nutrients and markets is in demand. Proteins from traditional sources such as soy and wheat, seeing potential value in other protein-rich legumes, seeds, or even leaves, have been considered as sources over the past 20 years in approximation. The extractions can be done traditionally by thermal or alkali methods, while other novel techniques, including ultrasonication, fit the need to improve extraction efficiency and better functional properties and less energy-intensive. Ultrasonic-assisted extraction (UAE), mostly applied in alkaline conditions, and aqueous extraction with variations, have improved yield and better functionality in most plants, compared to the traditional alkaline method. In practical use, multiple established methods are applied together to accomplish the best results, apart from limitations. The review aims to examine the data from these results and to provide general evidence of availability, meanwhile mentioning some definite challenges in real manufacturing environments. Regarding its better applications to manufacturers, possible guidelines in practice are presented.