if you get the Patreon build, you can enable cheats, then meet any character, and all the gallery will be automatically open
You don't need to meet a character, if cheats are on, it unlocks it all anyways. Also if you have a previous patreon build, you can turn on cheats for that build, and when you open your new one (not patreon build), it will have it all unlocked(cheatmode will be on, to turn it off again you have to go back to the old one to turn it off.)