You gotta remember not everyone is paying attention to this page every day. There is a discord where most people are active and answer questions.
As for your question, here is a guide that details all you need to know including how to accomplish endings.
https://mega.nz/file/KdkiiSBT#_rjQUv6QP3uYBddeK6XW4dumDoviQwIqGKBZiZAE2j8
Drakyle
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If the Soulless route is started you'll see it at the start as Unknown will ambush the person trying to knock on the front door.
https://mega.nz/file/KdkiiSBT#_rjQUv6QP3uYBddeK6XW4dumDoviQwIqGKBZiZAE2j8 here is a link to a guide, i dont know how much more ways I can try make it clear, encounter unknown, go through the sequence until she asks for your soui, give it to her, re-open the game and load the save file for the fun you was in when you triggered her, complete an ending and you should see Unknown in the post credits. If she appears then it's time to make a new game and watch the fun unfold.
A 3rd and final update is being worked on for Anne
The ending largely doesn't matter as long as it's one of the 3 core endings (not soulless or artifact) and that you gave her your soul then reload the save if Unknown appears in the cahtedral you find the original Anne's soul and/or after the game end sequence then ya know it is working, from there just hit new game and unknown will do her thing.
You can use a screenclipping tool like gyazo or such to easily take an image and provide a link to show it. However, i'll break down the sequence of events you should see and you can tell me if a step isnt happening just to be sure.
Unknown eats you in the corridor
She closes the game.
You open the game and she appears with a big belly and demands a belly rub.
You rub her belly, multiple times until she asks for your soul.
Accept and she'll close the game again.
Open the game, it'll run like normal, but if you complete an ending she'll appear.
After this occurs run a new game and the start will change.
As for artifact: https://gyazo.com/e2fb91f14be968ff126c409250da80a1
The artifact needed to call the numbers that make the artifact ending items trigger is found in that, east path after going through the gate where you use the snake, person and stomach tokens to create a scenario. (west path goes to the school area)
Artifact only can be acquired AFTER beating the game at least once, you pick it up from the pond thing when you go east after getting outside instead of west which leads to the school.
Unknown is the nude brown/chocolate coloured spirit.
Keep in mind if you are trying to accomplish everything in joiplay, it is not supported for this game and will not work for Unknown.
Here is a link to the guide for the game, it should help you out: https://mega.nz/file/KdkiiSBT#_rjQUv6QP3uYBddeK6XW4dumDoviQwIqGKBZiZAE2j8
It is possible to trigger it if Anne up until that point has been behaving strongly like a Gutslut and then apologises for not digesting to Rito, with enough Gutslut points, she will offer you to 'correct' it and if you dont back out you then get 4 options of how she will make Anne her prey, though by completing the game once, you can view that game over from the Gallery anyhow.
Gutslut behaviour is stuff like not resisting Mika in the maze (since Nala saves you regardless) and interpretting the tokens as 'Snake Devours Woman'
After completing the game once, load up a save that hasn't seen the Piano scene with Mika and Nala yet and go into the outside area of the mansion, instead of heading left like normal go right and you will see a sparkle in an area near to a wall at the back. Normally you can't get it but after beating the game you can, it is the 'artifact' using it will generate a Hello.txt file in your folder, translate it using base64 converter for 4 phone numbers, the first 3 of them will lead you to locations where memory fragments can be collected, the final one when you have the 3 memory fragments, unlocks an option to walk away after unlocking the basement. Doing so triggers the Ending
I have no experience with joiplay so i cannot speak with any certainity to a fix to this and i dont know if this bug has been raised to the attention of Cinna but i'll make sure it is, but in the meantime, one thing you might try is seeing if uploading your savefiles (including the config and globals) and having someone not on joiplay load them and see if that allows for the game to get past the issue you are stuck on, honestly im not sure which file it's calling out to when it has to flag what phase of the interruption by Unknown that it has to be at but i'd think one of the files in your saves folder is a safe bet.
The chase can't happen until you get the clock hands normally, there is a guide someone made if you wanna rely on that for specific details
https://mega.nz/file/KdkiiSBT#_rjQUv6QP3uYBddeK6XW4dumDoviQwIqGKBZiZAE2j8
I don't believe this prompt appears in the new version, Gutslut can be accomplished by never resisting Mika during the dream or in the labyrinth, by not resisting the Marie in the surgery room, by apologising to Rito for not being digested by her (but dont accept her offer as thats a game over), by telling Nala you'd let her eat you in the chat that occurs after escaping Mika when returning from outside, by interpreting the coin puzzle to mean 'Snake Eats Woman' and dont resist when the hungry maid pretends to want to eat you as seconds or when the shoe ghost pretends she is going to digest you in order to take a convincing photo.
It is the girl who lost her shoe in the ball room you need to talk to, she temporarily eats you to take a picture with you in her belly as the proof, if ya been gutslutty she will tease about eating you when ya first talk to her but after denying her should proceed to help you. Keep in mind you first need to be asked to get proof by the angry ghost in Anne's Bedroom
https://aryion.com/forum/viewtopic.php?f=79&t=62945&hilit=devoured a link to where the download link for Devoured is found (the download link is on mega but so you can see the content it would have and stuff, this is the page for the creator's games)