Phone manufacturers normally stop updating their phones after a couple of years. They do this to minimize the amount of phones they need to worry about, and also, you guessed it, planned obsolescence.
This doesn’t mean that your phone can’t be updated – far from it.
A awesome team of devs launched something called CyanogenMod a couple of years ago, which is a project that is meant to replace old Android versions of no longer supported phones with custom new ones.
That project has now been renamed to LineageOS, but for the end user it essentially does the same and focusses on bringing new Android versions to old phones.
Since those projects depend on devs porting the so called ROM’s over to other phones, if your phone isn’t well known ‘in the world’, the chance is lower that you’ll find a ROM for your phone. However, if your phone is a “Galaxy S6/S7” or another one which is well known, the chances are high that you’ll find a ROM for your phone, probably even more than one to choose from.
You can try Googling for “<phone model> Lineageos” or “<phone model> Cyanogenmod” and you’ll find out pretty fast. Instructions on how to put those on your phone is written on the page(s) itself.
Good luck 🙂
