itch.io

(On Android) open "my files" app, press "internal storage" then press "android", then "data", scroll till you find "harem.hotel" and press it. Copy all the save data in that folder either to a cloud storage or other storage area (eg. SD card) delete HH from your phone, download the latest version, install it, then follow the same path and put your saves back in the save folder. I don't have an iPhone so can't help you with that unfortunately.

Oct 23 for $20+ patreon supporters, Oct 30 for $5+ supporters and free release on Nov 6 (there's a reply post from like a week ago from Komisari confirming that, just scroll down far enough, you'll find it)