Hello. I can't get GEM to work on MacOS Catalina (10.15.4). I installed using Help > Find Externals. Here're the errors I get. . . .

/Users/jbohn/Documents/Pd/externals/Gem/Gem.pd_darwin: dlopen(/Users/jbohn/Documents/Pd/externals/Gem/Gem.pd_darwin, 10): Library not loaded: libfreetype.6.dylib
Referenced from: /Users/jbohn/Documents/Pd/externals/Gem/stuff/lib/libftgl.2.dylib
Reason: image not found
/Users/jbohn/Documents/Pd/externals/Gem/Gem.pd_darwin: dlopen(/Users/jbohn/Documents/Pd/externals/Gem/Gem.pd_darwin, 10): Library not loaded: libfreetype.6.dylib
Referenced from: /Users/jbohn/Documents/Pd/externals/Gem/stuff/lib/libftgl.2.dylib
Reason: image not found
/Users/jbohn/Documents/Pd/externals/Gem/Gem.pd_darwin: dlopen(/Users/jbohn/Documents/Pd/externals/Gem/Gem.pd_darwin, 10): Library not loaded: libfreetype.6.dylib
Referenced from: /Users/jbohn/Documents/Pd/externals/Gem/stuff/lib/libftgl.2.dylib
Reason: image not found
GEM: Graphics Environment for Multimedia
GEM: ver: 0.94.git v0.94_pre1
GEM: compiled on Dec 21 2018
GEM: maintained by IOhannes m zmoelnig
GEM: Authors : Mark Danks (original version)
GEM: Chris Clepper
GEM: Cyrille Henry
GEM: IOhannes m zmoelnig
GEM: with help by Guenter Geiger, Daniel Heckenberg, James Tittle, Hans-Christoph Steiner, et al.
GEM: found a bug? miss a feature? please report it:
GEM: homepage https://gem.iem.at/
GEM: bug-tracker https://bugs.gem.iem.at/
GEM: mailing-list https://lists.puredata.info/listinfo/gem-dev/
GEM: binary/abstractions version mismatch!
GEM: continue at your own risk...
GEM: compiled for MMX/SSE2 architecture
GEM: using SSE2 optimization
GEM: detected 8 CPUs
GEM: image loading support: magick SGI imageIO jpeg tiff
GEM: image saving support: SGI imageIO jpeg magick tiff
/Users/jbohn/Documents/Pd/externals/Gem/gemcocoawindow.pd_darwin: dlopen(/Users/jbohn/Documents/Pd/externals/Gem/gemcocoawindow.pd_darwin, 10): Symbol not found: __ZN9GemWindow3keyEiNSt3__112basic_stringIcNS0_11char_traitsIcEENS0_9allocatorIcEEEEii
Referenced from: /Users/jbohn/Documents/Pd/externals/Gem/gemcocoawindow.pd_darwin
Expected in: flat namespace
in /Users/jbohn/Documents/Pd/externals/Gem/gemcocoawindow.pd_darwin
/Users/jbohn/Documents/Pd/externals/Gem/gemcocoawindow.pd_darwin: dlopen(/Users/jbohn/Documents/Pd/externals/Gem/gemcocoawindow.pd_darwin, 10): Symbol not found: __ZN9GemWindow3keyEiNSt3__112basic_stringIcNS0_11char_traitsIcEENS0_9allocatorIcEEEEii
Referenced from: /Users/jbohn/Documents/Pd/externals/Gem/gemcocoawindow.pd_darwin
Expected in: flat namespace
in /Users/jbohn/Documents/Pd/externals/Gem/gemcocoawindow.pd_darwin
gemcocoawindow
... couldn't create

Gem is working for me under OSX Catalina 10.15.4.

I see you have installed Gem v0.94_pre1 from 2018, you should use:
GEM: ver: 0.94.git v0.94
GEM: compiled on Feb 12 2019

Also with my computer I needed to change [gemmacoswindow] with [gemglfw3window] inside [gemwin] abstraction for it to work.

How does one change gemmacoswindow with gemglfw3window? Is there a tutorial somewhere on this?

1 - Create a [gemwin] box
2 - CMD + F (OSX) or Ctrl + F (Windows / linux) to open the search box
3 - Paste: gemmacoswindow and type enter to search
4 - replace gemmacoswindow with: gemglfw3window
5 - save change to gemdefaultwindow.pd

Now creating a window with Gem might be ok.

@60hz Thanks for the info.