Well I have had this same problem now since last December and have been getting really fed up with the whole issue and the inability for Microsoft to fix it. Have had various issues getting updates to install until I heard about the issue with .net Framework 3.1 which I disabled and eventually then managed to get updates to install. Have left it disabled ever since and so far not had any problem. So I then assumed that the original indexing issue with Win11 and Outlook 365 would also be solved. So Rebuilt the index which took days (left the PC on permanently). Index rebuilt and though all was good - no such luck as unindexed items just started to increase by the hour.
Now came to 22H2 update which after a few attempts eventually installed and then I noticed that there were a further 3 updates waiting to be installed so set them off and they eventually installed.
after 22H2 installed I noticed that the index had been restarted and was rebuilding - slowly. So left PC on with sleep set to 'never' and after a few days the index was completed and 0 items waiting to be indexed both in Wil11 and Outlook.
Its been over a week now and indexes still seem ok with 0 items waiting to be indexed. Did have a worry a couple of days ago when I noticed that there were over 4k items waiting to be indexed - but leaving it working over night and all had been indexed by morning.
Am not sure that the issue has finally been fixed - I did say that once before and it hadn't been - but things are looking a lot better than they have over the last 10 months !! Fingers and everything else crossed