The reason is that FileMaker Server uses FreeType library.
DynaPDF also uses the FreeType library.
But those are not in the same version or with the same configuration.
So data structures are not in sync.
This is not a big problem on Ubuntu 18, but on Ubuntu 20 this crashes when DynaPDF renders a PDF document.
You can download the 64-bit Linux version from DynaForms directly.
Take the .so file from the archive, rename it if needed and upload to the Linux server.
We include the new libraries of course as part of the upcoming 12.4pr1 version of MBS Plugin.
PS: This is not a problem with our DynaPDF plugin for Xojo since we fixed a similar issue years ago for all our Xojo plugins.