It used to be Digicert, but they hit the rock bottom and went straight below it after their merge with Symantec. Quadrupled their prices by forcing everyone on subscriptions, obnoxious sales people, sales phone calls, price negotiations, the whole shebang. However, their validation team is still the best.
It took some searching, but it turns out that they spun off their non-subscription certificate business under the name of GoGetSSL. This entity resells other vendors too, but if you get their "own" certificate, which is the cheapest of the bunch, the validation is done by Digicert. So, that's the answer for the time being.
Entrust, Globalsign, Certum are way more expensive, slow and bureaucratic. Comodo (or Sectigo, which is the same thing) are just utter crap. Their validation process is an India-outsourced torture. Never again. Not even for free.
It took some searching, but it turns out that they spun off their non-subscription certificate business under the name of GoGetSSL. This entity resells other vendors too, but if you get their "own" certificate, which is the cheapest of the bunch, the validation is done by Digicert. So, that's the answer for the time being.
Entrust, Globalsign, Certum are way more expensive, slow and bureaucratic. Comodo (or Sectigo, which is the same thing) are just utter crap. Their validation process is an India-outsourced torture. Never again. Not even for free.