Thanks, I was going to do that, but nah there’s no actual need; I confirmed it’s the glibc issue mentioned above, and it can only be helped by building the modules again using a different version of that. Each XFX plugin logs “GLIBC_2.32 not found (required by [insert XFX plugin binary here])” after extraction.
In other words, the XFX modules are built using such a recent glibc version that it - probably unintentionally - narrows their compatibility a great deal. One rule of thumb (of many) when doing a closed source build for distribution is, if there isn’t actual need to go with a newer version of glibc, it’s probably a good idea to check which one is used in the most recent official Debian release (currently glibc 2.31) and at least stay within that.
VCV Rack 2 system requirements say “Linux (such as Ubuntu 16.04+)”, and that would actually mean glibc 2.23. The one used in these modules isn’t even in the latest LTS release of Ubuntu, 20.04 LTS, which uses 2.31.