Since UE5.0.3, the “Select” option, when pressing the right mouse button on an object, is gone.
It is in the top Menu bar.
Please add an option in the Editor Preferences to enable it through the RMB Button again.
So it won’t disturb your intended “Right-Mouse-Button Menu”, and those who want it, can still access it via RMB.
Looking forward to hear from you.
UE4:
UE5: