If you are starting from post 1 in a thread?
next to the post number on the left is a narrow pale blue cursor. Drag that down and you can go to the last post, in one move.
If you are going from the new post menu on the right of the home screen?
There is the post number and a time or date on the right. Click on the post number and you get the choice of first or last post.
Three are some other (hopefully) helpful posts here. New site 2024