Summon Undead cannot be stored in Glyph of Warding.
Glyph of Warding says:
Spell Glyph. You can store a prepared spell of 3rd level or lower in the glyph by casting it as part of creating the glyph. The spell must target a single creature or an area. The spell being stored has no immediate effect when cast in this way. When the glyph is triggered, the stored spell is cast. If the spell has a target, it targets the creature that triggered the glyph. If the spell affects an area, the area is centered on that creature. If the spell summons hostile creatures or creates harmful objects or traps, they appear as close as possible to the intruder and attack it. If the spell requires concentration, it lasts until the end of its full duration.
While Summon Undead description has:
Range: 90 feet
...
It manifests in an unoccupied space you can see within range.
Having a range of 90 feet it targets a point, not an area, and also not a creature, so it can't be cast into Glyph of Warding.
Even if you consider targetting a space is targetting an area for the purpose of Glyph of Warding, the Glyph of Warding also says:
... If the spell affects an area, the area is centered on that creature.
So it is targetting an occupied space, and hence Summon Undead fails anyway.
Perhaps you ask, "but there is a clause about if it summons a hostile creature!", and to that I respond, the Summon Undead isn't specifically hostile to anyone. It just states that it's ally to you the caster. What it does depends on what commands you give to it. See also this question to see that people didn't consider there is any spell that fulfills the Glyph targetting condition and summons at the same time.
A few other potential blockers against this idea:
- Familiar can't speak, so can't issue orders. But perhaps a warlock familiar can.
- Glyph of Warding doesn't make the familiar the caster. I'm not sure who is considered the caster, you or "the glyph", but definitely not the familiar.
- Typically extradimensional space is considered at infinite distance, so moving glyphed object in or out of the Bag of Holding destroys it. That's why typically the way to activate it is for the glyphed object to stay inside the bag, and you set the trigger as "when I insert my hand into the bag with specific gesture" or something.
- Taking out item from Bag of Holding is an action, not free item interaction.
