Right, it hasn't made it in v2. As a workaround you can copy-paste the automatically created cron entry to the job scheduler of your choice, it will work just fine. But don't forget to disable built-in scheduler in the job settings.
Also, I'd like to share some concerns that I have regarding the subject. Job schedulers like anacron and systemd-cron/systemd-timers allow users to implement advanced schema (like run missed backup, for example), while cron does not provide such flexibility. Thus, if we decide to leverage alternative scheduler(s) to support advanced scenarios, that will mean that some users won't be able to benefit from new features, which seems to be a little bit unfair
Maybe we should create a built-in job scheduler instead of trying to support all flavours of linux schedulers?