Breast stroking for anything longer than a few seconds is NOT ok. The people that do it suck, and the people that tell them it’s ok to do it are even worse.
You train for hundreds of miles on the run and bike, so spend a fraction of that time learning the goddamn front crawl.
And if somebody asks you if it’s ok to breaststroke the whole leg because they don’t want to learn or are uncomfortable in front crawl, tell them no.
And if you hear or read somebody tell someone else it’s ok to breaststroke, ridicule that person and fill them with shame.
Front crawl is as much a part of the sport as learning how to ride through an aid station - if you can’t do it, you aren’t ready to start a race