The API for viewing an instance timeline is public, there are some timeline viewers in the wild [0][1].

To view the local timeline for mathstodon.xyz one can use this link [2], even though [1] looks better (but can't use a direct link).

[0] - http://www.unmung.com/mastoview

[1] - https://m6n-view.hnle.tk/

[2] - http://www.unmung.com/mastoview?url=mathstodon.xyz&view=loca...