I had a presentation on what's new in SQL Server 2022 just last Friday (before it dropped). To have some demos, I've used Azure SQL Database to showcase the GREATEST, LEAST, WINDOW and STRING_SPLIT because it was already there
and Azure SQL Edge in docker had the IGNORE/RESPECT NULLS and DATE_BUCKET. No GENERATE_SERIES though
One common method is to use the VALUES clause, and CROSS APPLY the two columns aliased as a single column, then get the MIN and MAX of each.
SELECT MIN(x.CombinedDate) AS least, MAX(x.CombinedDate) AS greatest
FROM dbo.Users AS u
CROSS APPLY ( VALUES ( u.CreationDate ), ( u.LastAccessDate )) AS...