This is an update to my original problem with upgrading to v15, as the original post has been locked, so I thought I'll share the fix that Soti support gave that fixed our problem as I dont see any other posts about this issue.

https://discussions.soti.net/thread/has-anyone-experienced-sql-errors-when-updating-to-15-3-dacpac-dac-message-warning-sql72015

Summary TL;DR

So we had a SQL72015 error every time we tried to upgrade to v15.x from v14.5. And was told we had to wait for SQL 2019 support in v15.4, which we did, but unfortunately that still same error and could not upgrade. 

Logged new ticket with Soti support and after investigating the issue, they gave the following SQL fix that solved our issue.

Use the following SQL query at your own risk, this is what was provided to us to fix my issue. This may not work for everyone

1. Take server snapshot and db backup of your Mobicontrol server.
2. Launch SQL server Management studio and login
3. Right click on MobiControlDB and click on 'New Query'
4. Paste the sql query and execute it.
5. Restart MC services (Deployment Server and Management Server)

-----code----

DELETE FROM dbo.Container;
SET IDENTITY_INSERT dbo.Container ON;
INSERT INTO dbo.Container
( Id
, Name
)
VALUES
( 0, 'No Container'),
( 1, 'KNOX Container'),
( 2, 'Android Profile Container');
SET IDENTITY_INSERT dbo.Container OFF;

-----code----