The main thing to know is that, with a few important exceptions, Aleph loans, i.e. the records of individual loans, who borrowed items, where from, the date loaned and date returned, etc. did NOT migrate to Alma. There is an important exception here. Items that were either Lost or actively on loan during the conversion, had an Alma loan created for them and these loans are discoverable via Analytics.
When working in the Fulfillment subject area, as seen below, the loan counts and the loans you can discover by writing reports are only loans that were created in Alma, or the relatively few Aleph loans that were converted to Alma loans as described above. When using Fulfillment for counting numbers of loans, you will want to exclude any loans before July 1st. The loans have already been counted and are available from Aleph for FY21. Filtering on Loan Date being 'less than' 07/01/2021 will do the trick.
In short, for reports on loans and number of loans for FY 21 and before, use Aleph, Arrow and LRS. For reports on circulation activity on Alma, starting with FY 22, use Analytics and the Fulfillment subject area, perhaps with a date filter so you don't pick up these converted Aleph loans.
While the actual loan data did not migrate to Alma, item records migrated from Alma did retain the number of loans for the item that was kept in the item record itself (z30_no_loans). This data was apparently added directly to Analytics, because while the item loan counts in the Physical Items subject include this number everywhere I've checked, I cannot find it anywhere in the item record itself.
So if you are working in the Physical Items subject area, you can get reports of numbers of times an item has been loaned, which combines the number of times it has loaned in Alma with the number of Aleph loans from the item record.
So: Aleph circulation statistics, by year, by location, by material type. etc. are not available in Alma. The Aleph loan data captured in Alma for items that were actively loaned out or lost is not representative of all loan activity before July 1st, 2021. You can tell how often an ITEM has circulated overall: a count that includes Aleph loans, but you can't derive any other loan information (such as date) out of these simple counts.
Don't forget that this is only for physical items. Items like e-books that are no longer part of the physical inventory do not have item circ data from Aleph.
Of course, you can write all sorts of analysis on Alma fulfillment activities.
Remember that Aleph reports and data are available until June 2022 via Aleph clients, Arrow, and LRS.