Image fields at this time do not permit webp format. There's no functionality to toggle what is accepted or not for image fields. Since it's baseline now and something we use nearly exclusively on our site as well though we'll be reviewing enabling it, but we've to review carefully as I'm unsure if it'll work with client side resizing at this time.
forge.joomlapolis.com/issues/9538
Also made a feature ticket for CB Gallery.
forge.joomlapolis.com/issues/9539
Same for CB Activity when used as a link in a post.
forge.joomlapolis.com/issues/9540