Which does English “l” and “r” sound come under, an allophone or different phonemes?

The two l s in little are allophones - they're two different sounds representing the same phoneme (basic sound)/grapheme (symbol representing a sound).

Native speakers don't normally think about those two l s as making a different sound.

In Japanese, はげ can be pronounced haɣe instead of hage, so this is an example of g and ɣ being allophon In some languages like Japanese, r and l are allophones, so speakers don't think of them as different, and are more likely to use the wrong one.

In English l and r are not allophones, because they represent different phonemes.

A phoneme is the smallest sound component of speech. A syllable will often consist of more than one phoneme. Speech synthesis software operates by playing a sequence of phonemes to produce intelligible sounds.

Allophones are phonemes with differing sounds. For example, the B in trouble and bitter are considered to be allophones as they both consist of the plosive phoneme for B but are enunciated slightly differently.

While in English, the letters L and R have different phonemes - they sound different, in languages such as Japanese and Korean there is often a single phoneme whose sound is part way between the L and R sounds of English. This can cause confusion to both eastern and western ears.

As others have expressed, r and l are distinct phonemes in English since they can occur in exactly the same environment (lace vs race) and allow two words to be distinguished by that variation alone. Conversely, they are allophones in Japanese (let's call this Japanese phoneme R), for the opposite reason.

Japanese R will, to English speakers' ears, sometimes sound like an l and sometimes like a foreign r. The idea that Japanese R is "in-between" l and r is not accurate per se.

Indeed, when R is pronounced fast (as it usually is in natural speech), it sounds like a foreign type of r in English. English r is made with rounded lips and the tip of the tongue cannot touch the alveolar ridge.

On the other hand, a slowly pronounced R will sound like an l to English speakers. When the tongue rests against the alveolar ridge long enough for air to pass through the sides of the tongue, a clear l is produced. Except for the fact that English l is often produced with a curled tongue, this is for all intents and purposes the same as English l.

Whether the tongue flaps or stays against the alveolar ridge, and whether air comes through the sides of the tongue or not do not constitute distinguishing features of the Japanese R, but they are essential components of the l and r English phonemes.

Similarly, place of articulation is not a distinguishing feature of nasals in word-final position in Japanese, causing Japanese speakers to mix up done, dumb and dung.