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Those pre-launch market validation put-your-email-in-here pages should probably be called prospecting pages. I haven't been using those enough at all.
I used Baserow (https://baserow.io) as the backend for a tiny landing page built for NimbusWS (https://nimbusws.com). Yak shaving aside, building with Baserow was quicker, easier, and much easier to manage/administer than other solutions I might have chosen in the past.