Call to undefined method Drupal\system\Plugin\ImageToolkit\GDToolkit::getResource()

Experiencing the same issue. I'm guessing it's related to the deprecation of the "getResource" function?
https://www.drupal.org/node/3265963 →

I changed "getResource" to "getImage" in WebP.php, and that seems to do the trick. Patch attached for v3.x.

Confirming that v2.1.0 does not work with Drupal 11 due to this issue (see also https://api.drupal.org/api/drupal/core%21modules%21system%21src%21Plugin...)

v3.0.0-alpha2 does work with Drupal 11 but is still in alpha - would be nice to make a new release for v2.1 with this patch (so that it really is compatible with D11) or make a stable v3 release. Or both!