I think you'd have a much better time with something lighter than Mastodon if it's running on a limited system. If you are really looking to minimise requirements, Pleroma and its derivatives are unfortunately about the best for it afaik, though I certainly have plenty of misgivings. I'm personally partial to GoToSocial, and it'd be my go-to recommendation for any self-host atm unless they had specific requirements that made it unsuitable.