What is the best filter system for canon rf 10-20mm lens

[shadowsports]

I don't believe there is a lens filter available for convex lens.  

[normadel]

The lens has a gelatin filter holder built into it. You have to cut filters to fit the holder. See the lens manual, page 13:

https://media.the-digital-picture.com/Owners-Manuals/Canon-RF-10-20mm-F4-L-IS-STM-Lens.pdf

There aren't filters to put on the front of the lens. Such a thing would have to be a dome, like the front curvature of the lens. No such thing.

[Tommyboyks]

I know that you can’t put a screw-on or magnetic filter on the front of the lens. I was wondering about what drop-in filters people are using. Or, if they are using a filter holder that will allow a filter to be placed over the front of the lens like the one made by NiSi.