https://news.ycombinator.com/jobs is probably a good enough sample to answer that question. The answer seems to be Greenhouse and Lever.

(Some companies link to job descriptions on their own site and/or embed the ATS-hosted form in their site, but many of those use Greenhouse or Lever too. The companies linking directly to ATSes do seem representative.)

I moved my employer’s job board (previously Google Forms) to https://wrk.xyz/ a month ago.

‘Wrk’ tries to be an all in one solution and you pay when you scale hiring (each active job posting is $10/month)

Also check out https://app.ashbyhq.com/product — I haven’t used this personally, but from what I’ve seen they’ve also built out an “all in one” platform pretty quickly and are still building fast.