Prevent specific User Group from deleting files in a specific folder

I’m on Nextcloud 12.0.2 on an Ubuntu server and would like to prevent a User Group from deleting files in a certain folder.

To clarify:
We have 1 folder that is for projects and contains drawings/schematics/information for the installers who go there, so they can easily get all the info they need without having to drag all the paper with them. Also if they encounter anything weird there they just take a picture and upload it in another folder.

In the past we had a few times someone deleted a file by accident. While i can use the deleted files for that, i have to log into their account to do it (cannot see a way to see all deleted files).
And sometimes we dont see that the file is missing for a long time. Then its hard to figure out who did that.

Any ideas on that? I tried looking in the apps but something like File Access Control just allows for blocking when someone has access / can upload and not block delete.

You could just send a share link to members of that user group, without actual access to the folder. They would be able to view the files, without being able to delete or make changes to it.