Almost all the servers on Mastodon and the wider Fediverse are run by unpaid grassroots volunteers that pay their server's bills out of their own pockets.
They don't sell your data or carry advertising, and they don't get any share of the donations given to the Mastodon etc software developers.
Please consider donating to your server admin, they usually have donation links on your server website's "About" page. You can also ask your admin directly about how to donate.