You asked
What are the alternatives to the canon rf 200 800mm f 6 3 9 is usm?
I don't have a list of other lenses to compare against the Canon RF 200-800mm f/6.3-9 IS USM, so I can't name direct alternatives from the catalogue yet. What I can do is point you to the reach advice on the Wildlife and sport page. There, a 100-400mm zoom on APS-C gives roughly the view of 150-600mm on full frame, and the 200-600mm and 150-600mm zooms are the usual full-frame answer for birds and fast sport.
My own picks are on the Wildlife and sport page, and I'd suggest a used copy of any of them. Long lenses hold their value, so the savings are real. The buying used page explains how to go about it. If you want to stay with the 200-800mm's mount, the Canon RF page lists the lenses that fit.
Written by Claude from this site's pages.