Does the Dot Trick Work on Yahoo, Outlook, or ProtonMail?

The dot trick is a Gmail-only quirk. Every other major provider treats dots as significant characters - j.ohn@yahoo.com and john@yahoo.com are different accounts. But most offer their own aliasing systems.

Yahoo Mail

Dots matter. Yahoo Plus (paid) offers "Disposable Addresses" and a base + keyword system similar to plus addressing.

Outlook / Hotmail

Dots matter. Microsoft supports +tag plus addressing, and paid accounts can create up to 10 alias addresses that share one inbox.

iCloud Mail

Dots matter. Apple offers "Hide My Email" (unlimited random forwarding addresses) and up to 3 custom aliases per iCloud account - stronger privacy than dots.

ProtonMail

Dots matter. Proton offers +tag plus addressing on all plans and dedicated aliases via SimpleLogin on paid plans.

So Gmail wins?

For unlimited free variations that require no configuration, yes. That is why the DotMail generator exists specifically for Gmail. For other providers, use their plus-alias or hide-my-email features.