Unfortunately due to limitations with SteamVR Input it's not possible to fix this issue.
VR InputAction returns wrong Key.
Did not reproduce with Rift
Confirmed in 4.26 MAIN @ CL 11451261
Prerequisite: Steam VR
Result: With only "Vive (L) Trigger" assigned to the action mapping, the correct name will print.
4. Add "Oculus (L) Trigger" to the action mapping
Result: Key name "Oculus (L) Trigger" will now print (If using the VR Template, "Mixed Reality (L) Trigger" prints)
There's no existing public thread on this issue, so head over to Questions & Answers just mention UE-88860 in the post.