Phyllis Coates originally played Clark Kent’s colleague and Superman’s No. 1 gal, but when sponsorship for Season 2 took too long to secure, the busy actress became unavailable to continue on as Lois Lane.

Noel Neill, who had played the Daily Planet reporter in a pair of Superman film serials, stepped in and got the job done for the next five seasons.

https://tvline.com/lists/recast-tv-roles-explained/adventures-of-superman-lois-lane/

Lois Lane Is a DC Comics Icon, But Noel Neill Is Her Best Live-Action TV Portrayal (https://www.cbr.com/noel-neill-best-lois-lane-television/)

Noel Neil cemented many of Lois Lane's fundamental aspects in the classic Adventures of Superman TV series and influenced every Lois performer since.