How can I generate a link to a specific email?

No, that is it correct. Onenote method works also using the desktop outlook app. At list the new outlook that I use.

Second method also works, but is a bit more complicated in my opinion.

I also found what is to me a fairly easy way (while I still think there should be a native way to do it).
I create a task from the e-mail. This task contains a deep link to the e-mail. Then delete the task if desired.

The only solytion I have found to that problem is :

1. Choose the "Send to Onenote" option for the email you want.
2. Go to the new note that has been created in the Onenote. There, within the new note, you will see the "link to outlook" option.
3. Put your mouse on that link , press Ctrl +K and get the link you are looking for from the window that will open.
4. Then , optially , you can delete the note on the Onenote.

Thanks @MrjB_79 That "link to outlook" was exactly what I was looking for. It's a shame you can't get this directly from the Outlook app. Why go through the hassle of sending it to OneNote, copying the link, deleting the note, then pasting the link where you want it.
*facepalm*.

My goal was to send an approval request and include a link in the approval details. Reviewers can access the email directly in their web browser by clicking the link in the approval request.

I achieved this via MSFT Automate.

1. I used the Send an HTTP request action in Automate
2. URI is something like https://graph.microsoft.com/v1.0/users/{user_email_address}/messages/{email_message_id}
3. Method is GET
4. I used the body('Send_an_HTTP_request')?['weblink'] expression to get the weblink for that specific email.

Couple of things I observed.

1. For anyone to see the email, anyone should also have at least read permission on that Inbox. You can do this via Outlook web or desktop.
2. For me {user_email_address} is my service email address, I had to allow members of the on-prem distribution list for which I was building the process read permissions on my Inbox.
3. At the least I had to convert the distribution list to a mail enabled security group before I could grant them read permission access on Outlook Web

After a lot of research I found this post and it worked outstandingly well for me. Thank you!

I'm copying the URL Outlook website provides, but when clicking the link to once again open that particular email, it just opens the inbox.

Please requesting assistance, as having a URL to address is a quicker way to reference or find it, than to use the search tool box.

thanks!