The bug
When a shulker teleports, there are no teleportation or portal particles. (Compare to enderman and using an ender pearl.)
How to reproduce
Spawn a shulker.
Cause the shulker to teleport.
Notice that there are no particles when it teleports.
Linked issues
relates to
Attachments
Comments

Revised title & description to be more descriptive.
Can confirm in 20w48a.
Can confirm in 21w03a.
Can confirm in 21w05a.
Can confirm in 21w05b.
Can confirm in 21w06a.
Video attached.
Can confirm in 21w07a.
Can confirm in 21w13a.

Can confirm in 1.17 and 1.17.1 Pre-release 1.
Can confirm in 1.18.1.
Can confirm in 1.18.2.
Can confirm.