well I am pretty new to MX but I think the answer to flatpak is "no." But I did solve "the problem" using chatGPT, or rather it gave me very good info to help me find the answer. Brave installed with the MX Package Installer (mxpi) and pretty sure it did not use flatpak (I only vaguely know what flatpak is & that's ok for now). The command to firejail firefox is exactly that, so I assumed the command for brave is firejail brave, but I looked around the file system see that it is installed as brave-browser, and firejail brave-browser works! (& chatGPT mentioned how to use an alias or something like that -- I vagely recall that from the past) Once upon a time I had a better understanding of linux file system, I am very rusty, and ditto linux commands. I WILL be reading. Also good to know chatGPT is there with good info. When I ran CentOS ages ago, I never took the time to learn linux more deeply. Running (& learning) MX is FUN++