I was trying to build VTK version 9.1 using an external “fmt” library but I am getting a cmake configuration error where VTK wants version 8.1.0 of fmt but such a version does not exist according to the official GitHub repository. There is however a 8.0.1 version of fmt available? Is this a bug in VTK or is VTK using some unreleased version of FMT?
We submitted a PR to fmt that has not yet been released. The comment on the requirement has more details.