common - something that happens frequently, something that isn't unexpected, something normal, can be used with people to mean they are normal/uninteresting/middle or lower class (compared with people of high socioeconomic class)
commonplace - same meaning as common, usually not used on people
widespread - something that is present in many places, even if it isn't common. COVID19 is widespread right now, but I wouldn't call it "common" because it is outside of what is normal.
Prevalent - something very noticable, generally accepted/practiced. More specific than widespread, usually used in reference to a specific location/country/city/group of people.
Rife - same as prevalent/widespread, but more negative in meaning. "Rife with corruption" is a common usage. If somewhere is rife with something, that something is bad.
Frequent - happens often, more number-focused than common. Only works with events. You can't say objects or people are frequent, you have to say that they are common. Ex. The meetings are frequent -> this means they happen often.
ubiquitous -> something that can be found everywhere, or practically everywhere. Ex. In America, fast food restuarants are ubiquitous. Means the same as common, but it's more extreme. It's like a combination of common and widespread.