Custom crm

My boss doesn't want to use an external app so I have to use what we got in hands as a CRM. (Wanted to suggest Zoho but he didn't want)

So I'm wondering what would be the best "app" to use as a CRM

Right now, I'm doing kind of a setup in an excel but I would like to setup some automation eventually and excel seems kinda limited for that. (Automation like automatic emails, fields getting updated , etc)

What do you think I should use ? I've been told there was many MS tools that could get this done Like ms list ?, dataverse ? Access ?

Note that, I'm not a programmer but I can handle my own with technologies. As long as it's not pure programming, I'll handle

Thanks!