Flex is another cloud based solution, however it requires the now obsolete Flash to be installed, so it causes problems for devices like iPads or iPhones, and as Chrome and many other browsers do not support Flash, we had to grade this accordingly. Flex have been promising an HTML5 version for many years now (since 2018), however other HTML5 apps are already available, meaning Flex will always be playing catch-up.
Flex have released Flex5, their HTML5 version that works without the now obsolete Flash, however it is incomplete and not very functional, thus Flex5 didn't make this list, as to do some things, you have to go back and use the Flash version.