in a new site, I’m using a new plugin – Qubely – from gutenberg editor.
The column don’t work, please look here: http://prntscr.com/om30l2
I have 2 columns. It doesn’t work with 3 or 4 either, the last column is below.
Some themes add the box-sizing: border-box; to ALL elements on the page, which can conflict with elements that require the default box-sizing ( as well as being poor coding ) hence GP doesn’t add it. You may want to feedback the the above CSS to the plugin author.