Both Uses of

competent
in
David Copperfield

I am aware that I am merely a female, and that a masculine judgement is usually considered more competent to the discussion of such questions; still I must not forget that, when I lived at home with my papa and mama, my papa was in the habit of saying, "Emma's form is fragile, but her grasp of a subject is inferior to none."†
Chpt 28-30

competent = sufficiently capable

With your branch of the subject, on which alone you are competent to speak, I should not think of interfering.†
Chpt 40-42 *

Definitions:

(1) (competent)
capable (able to do something in a generally satisfactory manner) -- sometimes specifically to have legal capability
(2) (meaning too rare to warrant focus)
meaning too rare to warrant focus:

In the field of law, competent has the specialized meaning of being legally qualified to do something such as to be mentally fit to make reasonable decisions; or to have jurisdiction or authority to take an action.

In classic literature, a competency can refer to having an income or assets to support living expenses.