How to install gimp-avif-plugin ?

[Ofnuts]

If this is only to convert images, have you tried ImageMagick. As simple as

Code:

convert PNG.png Example.avif

If I do the conversion both ways (PNG > Avif > PNG) and compare the two PNG (histogram of the difference between the two images), they are strictly identical.

Note that AVIF is a very new format, support can be buggy, and the bug can be anywhere in your toolchain, the conversion, or the browsing.