For professional projects I have worked on, the rule of thumb we have landed on is usually to support 2 versions older than the current version. Yes it's usual

For professional projects I have worked on, the rule of thumb we have landed on is usually to support 2 versions older than the current version. Yes it's usually a small minority of users who haven't upgraded, but that tends to be people with older phones who can't update to the latest version. It makes my life harder, but it's better than punishing users who can't afford to upgrade their phone often.