I'm going the plug Clockify as a happy (unaffiliated) user. It's free for small users, and has a good reason for how they make money anyway (it's just advertising for them, they make their money from big customers like Google, IBM, PwC). They have everything and the kitchen sink, but you don't have to use it. For example, open an email or a Google calendar event or a Github issue and they've added "start tracking a new task" inline.