Can you gain muscle doing only isometric exercises?

https://onlinelibrary.wiley.com/doi/10.1111/sms.13375

English, full-text, peer-reviewed journal articles and unpublished doctoral dissertations investigating medium- to long-term (≥3 weeks) adaptations to isometric training in humans were identified. These studies were evaluated further for methodological quality. Twenty-six research outputs were reviewed. Substantial improvements in muscular hypertrophy and maximal force production were reported regardless of training intensity.

Skeletal muscle hypertrophy in response to isometric, lengthening, and shortening training bouts of equivalent duration

https://www.t-nation.com/training/isometrics-for-mass/

https://liftbigeatbig.com/isometrics-for-strength-hypertrophy/