@Indic Software ABM is a wrapper for Materialize CSS, no other CSS framework (Bootstrap has nothing to do with ABM). If you want to use that, I wrote the BANano library, where you can use ANY css/javascript framework (Bootstrap, ReactJS, Vue, ...) you want.
ABM is in many cases the perfect tool for WebApps, without having to know anything about Javascript, CSS, HTML, PHP or Web whatsoever. Knowing pure B4J is enough. It is used internally within our company and has dramatically increased the development speed over any other tool we used before. THAT is the reason I shared this library to the community.
ABM does a lot of stuff in the background that makes the resulting app fast and reliable because it prevents the programmer from making common mistakes. The B4J Webserver Jetty is a very good Webserver and, with the proper load balancing, can serve up many users (just the same as with ReactJS, NodeJS, PHP: without a good load balancing strategy, they also will choke on a huge number of users just like Jetty will). In our latest company ABM WebApp, it will serve up to 50.000+ users with ease.
So the choice is: learn Javascript/HTML/CSS/PHP/ReactJS/Bootstrap/Vue and do all you want, or use only one language B4X where you are familiar with, having Materialize CSS as your UI with ABM (and some custom components if you want to pimp it a bit).
I guess as you already know html/javascript/css/php very well, your choice is simple and ABM just isn't for you. But I'm glad it has given many B4X users the opportunity to make great, robust WebApps without having to learn new stuff.
Alwaysbusy