Of course you can have an employer sponsored 401(k) as an employee and also have a Solo 401(k) as a business owner.
See this website for information - https://www.investopedia.com/ask/answers/100314/do-i-need-employer-set-401k-plan.asp#:~:text=If%20yo....
And - https://meetbeagle.com/resources/post/can-i-have-a-solo-401k-and-a-regular-401k
