FL20.5.0.1142 installed into Win7 bottle in Crossover 18.5 - Linux Mint 19, XFCE . Both the 64-bit and 32-bit versions of FL20 appear to run successfully 'out of the box' (deslelect installation of Asio-for-all), though the installer creates 2 launchers for the 64-bit version and none for the 32-bit version. I used the Run Command to create a launcher for the 32-bit version.
Plugin 'bridging' seems to fail and crash the system consistently. I prefer to avoid this by installing FL into a Win7-32 bottle (so the installer skips all the stock 64-bit VSTs) and use this for most of my work, and install separately into a Win7-64 bottle only for projects that require 64-bit VST's that don''t have 32-bit alternatives (being careful to avoid adding any 32-bit plugins to the project).