For customer-hosted Looker instances, customers need to manage the chromium installation themselves. This is different for Looker-hosted instances as those are managed by the Looker Team.
To learn more about it and how to install it for customer-hosted Looker instances refer to this Official Documentation
There has been some issues with the rendering process (From timeouts to incomplete renders) when rendering Looks or Dashboards to PDF/PNG formats.
To avoid these issues we recommend to use Chromium 97. Avoid installing versions 98 and 99 as these ones will probably introduce rendering problems.
You can find the list of chromium releases on this page: https://chromiumdash.appspot.com/releases?platform=Linux