Note Kiso releases (3.0.x) are compatible with Drupal 10.
Kiso is a brand new base theme completely build from scratch. Kiso theme is fully built around and adapted to Drupal 9/10, with a strong focus on accessibility, portability, simplicity and efficiency.
In a nutshell:
Kiso supports the latest, stable releases of all major browsers and platforms. On Windows, Kiso supports Internet Explorer 11 / Microsoft Edge. (Although Internet Explorer 11 support dropped in Drupal 10)
Kiso implemented a time saving tool for developers. With this solution you can check if the user’s Microsoft browser can handle your website. If not, it will show a looking notice advising the user to update his browser for latest versions.
Alternative browsers which use the latest version of WebKit, Blink, or Gecko, whether directly or via the platform’s web view API, are not explicitly supported. However, Kiso should (in most cases) display and function correctly in these browsers as well.