Old tablets/mobiles with no OS/Android updates for about 5 years still work, getting sluggish though with modern apps and not enough ram.The real question is, whether Google Play Store and apps are updated?
While outdated Android is not ideal, most vulnerabilities are usually local.
I had "no brand" with no OS updates for 3+ years, but apps were updated.
GooglePlay is the important part, as long as the Play store works and you can update apps your fine. So far so good but updates are getting less frequent for old devices.
