The full solution is below, with a short explanation for each group. To avoid spoilers, play the puzzle or open the hints page before reading the answer panels.
ESCAPE, ENTER, SHIFT, and SPACE all fit the category "Computer keys". They are labeled on many keyboards. The shared link accounts for all four words, which is why the remaining board words should be tested against a different rule.
Category
Night sky
METEOR / VENUS / NEBULA / ORION
METEOR, VENUS, NEBULA, and ORION all fit the category "Night sky". Look up after sunset. The shared link accounts for all four words, which is why the remaining board words should be tested against a different rule.
Category
Coffee shop orders
AMERICANO / LATTE / MOCHA / CORTADO
AMERICANO, LATTE, MOCHA, and CORTADO all fit the category "Coffee shop orders". You can hear these at a counter before 9 a.m. The shared link accounts for all four words, which is why the remaining board words should be tested against a different rule.
Category
Things that fly
EAGLE / KITE / JET / DRONE
EAGLE, KITE, JET, and DRONE all fit the category "Things that fly". They spend time in the air. The shared link accounts for all four words, which is why the remaining board words should be tested against a different rule.