> I have already switched to AVIF on every platform I use that supports it, and WebP where AVIF isn't supported.

Where AVIF isn’t supported, I reckon you’re better to fall back to JPEG. Everything supports JPEG, but there are still plenty of things that don’t support WebP. Anything that supports WebP now has indicated it’s open to supporting newer formats than the baseline JPEG/GIF/PNG and is almost certain to support AVIF within a few years.