I just noticed that my earphones are quieter on the left than on the right. With my Bluetooth headphones (also ear) I had the same problem and thought / think they are broken.
My headphones: The cable headphones that always come with Samsung phones.
The bluetooth: F6 real wireless headphones
My phone: Huawei Honor play Android 9
Check an audio test on YouTube, if the headphones are wired clean the jack. Then test with another device. If that is still the case, they are probably actually defective.
There was the point "Balance", which controlled the right and left channels in stereo, and was normally fifty / fifty.
The same is also available in Win10: right-click on the loudspeaker symbol, then open the volume mixer, then click on Device - Loudspeaker, then Balance, here you can set the percent for all channels.
But I don't know whether this also works on a cell phone.
