How to get more chain tips from getchaintips? I've just restarted my node. When I run getchaintips, it only gives me 48 tips (the lowest being at a height of 402,609).

Does getchaintips only return a limited number of branch tips? If so, is it possible to get more branches?
It returns all branches your node knows about.

Note that your node cannot know anything about branches that occurred while your node was still syncing, as you only get the active best chain from your peers.

Also, if you are connected to a single node only for a while, then you will during that time not hear about any branches, as you only get to see the best chain as it is determined by your peer.