Here is one alternative:

   With validEmail (EmailAddress)
     As (
Select te.EmailAddress
   From #tblEmails       te
Except
Select tne.EmailAddress

Are you using temp tables - or are these permanent tables?  If permanent, then you are already dropping the table and recreating it every time...it probably would be better to...

Did you back up the encryption key from the old server and restore it on the new server?

Modify the ON to

On t.id = s.id
And t.startdate = s.startdate

then add a check for

When not matched by source
Then
Update
Set enddate =...

=Today.AddDays(0 - Today.Day)
=DateSerial(Year(Today), Month(Today), 1).AddDays(-1)

Alternative methods:
=Today.AddDays(1 - Today.Day).AddMonths(-1)  \\First of last month
=Today.AddDays(0 - Today.Day).AddMonths(0)  \\Last day of last month

=Today.AddDays(1 - Today.Day).AddMonths(-2)  \\First of...

How is the linked server configured 'to use a specified login'?
If you are adding a login named 'myuser' to MyLinkedServer - and then adding that as a user in...

I would recommend adjusting the configuration for the catalog first - instead of removing the logging.  Also - if you are running into space issues with SSISDB then you should...

Does the secondary have enough space available for the transaction log to grow?  I have run into issue where the secondary had 400GB drive - primary also had a 400GB...

Review the following articles:

https://www.brentozar.com/archive/2016/01/cheat-sheet-how-to-configure-tempdb-for-microsoft-sql-server/
https://www.sqlskills.com/blogs/paul/a-sql-server-dba-myth-a-day-1230-tempdb-should-always-have-one-data-file-per-processor-core/