In very general terms, angelfish should not be housed with linear fish as it is easy for these to be seen as food. This somewhat depends upon the temperament of the individual angelfish of course, and the size of the fish (both the angelfish and the linear fish). Most stores sell shoaling tetras as fry, and they are very small and almost inevitably going to entice the angelfish to see them as food. Fully grown tetras might fare better, but again it depends upon the angelfish.
Disk-shaped tetras fare better, and angelfish are not so likely to see them as food, though territory can play a part. Disk-shaped tetras like those in the "Rosy" clade, the Rosy Tetra, Ornate Tetra, phantoms, etc.
I should also mention that keeping the single angelfish contrary to its inherent expectations of being in a shoal can have a detrimental effect on the angelfish, and this can play out as increased aggression, or the opposite, or...whatever. I would also caution that the addition of any other cichlid species here is a risk for the same reason.