Obviously, shared with me folders are visible on the Google Drive web, but I cannot find them on my local Google File Stream. One suggestion online was to create a shortcut on my own Google Drive, but it didn't work. Any idea?
This is a recent change (from around April 2020). Previously, one was able to add files and folders from "Shared with me" to one's Drive. This made syncing other people's files with one's computer's hard drive easy. However, items can no longer be placed in more than one folder. This does simplify syncing, as far less data is used to sync a shortcut, compared to large items.
In addition, it prevents people from believing that other people's files are permanent. It is always possible for the other person to permanently delete their files (often this would simply arise from technical reasons, such as deleting their account, reducing storage, or accidents, rather than an unkind decision). To ensure that you keep someone else's files permanently, make a copy. If its parent is "Shared with me", right-click on the file and select "Make a copy". If its parent is a shared folder, select the files you want to copy, right click on the selected files and select "Make a copy". In both cases, the copies will be placed in "My Drive", which you should move to a sub-folder. Unfortunately, entire folders can't be copied at once using the features in the Web app, although you could download the folder, then upload it to your Drive, instead.
For files that are not Google Docs editors, when edit access is granted to other people's files, it appears that Google Drive now expects users to manually upload edits, through the Web app. (This is done by right-clicking on the file > Manage versions > Upload new version.) In my opinion, this makes collaboration more difficult compared to before, when items could be added to My Drive. An alternative is to use Github, or to use G Suite's shared drives.