There are 3-4 typical different approaches to rendering text on X. If it's not yet (or not correctly) implementing one or two of them, that'd explain it.

EDIT: Testing with xtruss shows st uses RenderCompositeGlyphs8(), part of the RENDER extension. I don't have Alacritty installed, but I think Alacritty uses the GPU, at least by default? Looking at the source for Glass it seems to use PolyText16 - the "old school" old server-side font rendering API. A lot of older X11 apps would work fine with PolyText16, and a lot of newer X11 apps does all the text rendering client side into a shared memory buffer without requiring GPU support, so it's not hard to end up with a set of applications where none of them would run into either gap.

EDIT2: I've looked at the Frame source, and it does seem to have support for the RenderCompositeGlyph calls and other supporting request, so not sure what the issue with st is. It's not doing anything unconventional.

I'd try rxvt (PolyText8/16) or xterm (ImageText8/16). If either/both works it's likely an issue with the RenderCompositeGlyphs support.