Is Bootstrap mandatory to build on Wappler?

Hi, I’m new to Wappler. I’ve been a previous user of Webflow and am accustomed to handcrafting my websites. I’ve never used Bootsrap before and wanted to know if I can do without it on Wappler. Just add my own classes and margins and custom scripts, if required. I tried removing Bootstrap from the front-end frameworks and somehow that makes the Theme Manager not work (Shows “If you want to use the Theme Manager, you need to enable it first in the Project Options”). I also read somewhere that Bootstrap is mandatory for App Connect. So just wanted more clarification on this?