Does it requires DB Admin account? I think no, but it requires user which must be able to execute all SQL scripts. These scripts require rights like create/update/delete over both your newly created databases and system databases.
CD_BROKER_CRETE_LOGIN.sql script in installation folder has following command:
IF NOT EXISTS (select * from sys.sql_logins where name='cd_broker_user')
CREATE LOGIN "cd_broker_user" WITH PASSWORD = 'cd_broker_password'
As you can see, it requires access to system databases (sys.sql_logins), so you must have these rights. In any case, I suggest you check all sql scripts in your installation folder and check if your uses has rights to execute them all.
SQL scripts are in
\SDL Web 8.5\Database\Scripts\mssql folder of your installation.
Official docs found here states that you need to be logged in as a user with sufficient security clearance.
Also, following page explains that system db admin must perform setup of SQL server. Besides this, following page states that following is required:
PowerShell scripts prompt you for the following information:
- DBA and user credentials (unless you created an Oracle SDL Web administrator user)
To answer your question in comment, no I don't think that that sort of list exists. I am afraid you will have to analyze all sql scripts and compile list of rights required by yourself. :(
Also, documentation states on multiple instances that DBA is required, so I guess you will have to request it.