Some fonts take forever to open in Glyphs. I don’t know what might be the reason in this specific case. The font is not large (1219 glyphs) but takes ~30 seconds to open in Glyphs, and during the opening, there is no indication that anything is happening at all.
spectral-regular.ttf (127.4 KB)
Once saved as .glyphs file, it opens in about 3 seconds.
Other TTFs are opened more or less instantaneously.