Since workflows have been removed from CMS v9, is there an intended alternative approach to implementing the equivalent (i.e. approval processes)?
IMO, the way to go are Episerver Projects.
It's a completely new approach, but more modern in terms of collaboration and while it still lacks some features (like workflows), this is, to my knowledge, planned. It gives you the possibility to work on parts of content in chunks, it's a good match for huge organizations, campaigns and generally any work in progress that needs to be published at the same time. Notifications work rather well and the whole look and feel seems more up-to-date. Generally, it's more collaborative then automatic at the moment (ex. when you are done with something, you would write: @marija.jemuovic, please review this project and I'd get an email).
You can enable projects on an Alloy tech project (from Admin -> Config -> System settings -> Editing), set up an SMTP server (you'll need that for notifications, I normally use smtp4dev locally) and play around a bit.
Thanks for your advice - I haven't dug into Projects yet so really should start playing!
BTW I often use debugmail.io which is a great free service for a dummy SMTP inbox.