They seem to use another service ( https://mangrove.reviews/ ) to save the reviews. On first read this does sound interesting and I will have a look at it. Thanks :)
Hm I might also check them in the future for reference. I would really like to have the TripAdvisor integration they have, but in a FOSS app. But I guess there would be some licencing issues.
For your personal use KDE Connetc might be best. But for "hey can you send me this" https://pairdrop.net/ is just magic. 0 setup and works on all devices with a browser.
One might want to also have a look at murena cloud. It's hosted in france, based on nextcloud and has the benifit of also including a mailing service. Additionally they have a custom andriod.
https://murena.com/workspace/
Dann wird dir das Preismodell von Mullvad gefallen :) https://mullvad.net/de/pricing (Evtl. für Deutsche wichtig: Da kann man auch Bar zahlen.)