IFS has now been updated to 1.21 and should have no trouble dealing with PaperMC (this seemed to be an issue with the previous version).
The default pricing file was also cleaned up a bit and updated.

Significant changes were necceary for this release and this causes some inconveniences:

• At first it will only support 1.21 (1.20 might work but is untested).
• Documentation has not been updated yet
• There are still some price calculation issues for items that involve wool somehow (beds, banners, carpet, ...)

For the above reasons this is still a beta release. Please test it out and let me know your feedback!