de_EDV

Preface: Sorry about the English, Ich kann Deutsch ein bisschen verstehen aber ich kann es nicht sprechen.

It starts getting dangerous to keep using it after security patches end. Especially when browsers and other apps stop supporting it, because then you won't get security patches for those apps too. This makes your phone more susceptible to viruses.

I would look into selling it or recycling it if you can't find any buyers.

If you like having your phones last a long time, I would recommend looking up Fair Phones. They promise to support their phones for a long time and give 5 year warranties. They also do many other things for social good, their website has more information on that.