Import a pst file into new outlook

I appreciate you sharing that information. What a trial this has turned out to be.

Doesn't apply to me. I have Outlook 2016 installed in addition to Outlook (new) app. 99.99% of the time I use Outlook 2016. I check Outlook (new) once a week or sometimes once/twice in a few months. Both apps are connected to the same mailbox, my work email. No other mail accounts in either app.

I believe what you described is how to install Microsoft Outlook/365 and Outlook (new). It sounds like the download is an ISO file which, when mounted, you'll get a virtual drive letter where you find setup or setup64 to run/install the software. If PST support on Outlook (new) requires Outlook/Microsoft 365 apps, that explains why I can't add a PST file in my Outlook (new) app. I don't have 365 apps.

Here's the answer that took me about four hours on Microsoft chat to figure out (and chat didn't help with a solution but showed me enough that I solved it myself). (1) you need to download the software package for offline installation. (from memory, and that's not what Chat said) (2) when you do it will create a fake drive that has (a) Setup.exe which will just do the same thing, install Outlook (new) not Outlook (classic) and also (b) a Folder that has Setup32.exe and Setup64.exe. It is only those setup files (technically I only used the 64) that will install both Outlook (classic) and Outlook (new). And it is Outlook (classic) that has the PST files. I turned out, I still had them on my drive and once I cracked the secret, they installed automatically.

I do have outlook.com but not connected to Outlook (new) app. I'm using the app to open work mailbox (custom domain name hosted on Exchange plan 1 service).

I'm not sure about that. I have two Outlook.com accounts, an E3, an E5, and three IMAP accounts in Outlook New, I have the Outlook Data Files selection, and I can verify it works for me. Do you have an Outlook.com account?