Testers open a link in their browser or scan the QR code with their phone. They create no account and install nothing, which is often what decides how much feedback you get back.
On screen, they move through the flow and fill in the fields. When something stops them, they click the section and write up to 1,000 characters, signed with their first name. You see the number of open comments and mark each one as resolved once it is handled.
The link stays private. You can renew it, which turns the old one off, or delete it when the test is over. To show two options to two groups, duplicate the project and share one link for each version.