Perhaps you might check these posts:

https://www.researchgate.net/post/What-are-alternative-repositories-like-arXivorg

https://academia.stackexchange.com/questions/84/preprint-services-other-than-arxiv-for-other-fields

https://academia.stackexchange.com/questions/37976/what-are-pre-print-repositories-for-math-and-physics-alternative-to-arxiv

https://www.researchgate.net/post/Which_platform_is_good_for_creating_preprint_of_an_article