For those using on-premise services the big shift is getting the majority of staff onto client VPN. Sometimes these companies haven't been using client VPN before, or it was only used by a small group (such as the IT staff).
Some companies will be embracing greater security at the same time as their risk profile from using machines at home is increased. So this may also involve rolling out things like Cisco Duo, Cisco Umbrella, etc.
Some companies may be using RMM tools (maybe even Systems Manager), group policy, etc to try and achieve this "at scale". Both computers and smart devices might need touching.
Some companies are taking the opportunity to move some stuff into cloud services, like Sharepoint, OneDrive, etc.
I think pretty much everyone is embracing collaboration tools, like Cisco WebEx, Microsoft Teams, etc.
Those companies that are already cloud focused often require very little change.
Some companies are also facing challenges around providing that physical work environment at people's homes. For example, having that second monitor. A desk, chair, basic things like that. Having an environment where you can concentrate without the children, dog, cat, etc busting in every 5 minutes.
There are also concerns about "safety in the workplace" - how do you make sure the persons work space is safe at home, how do you handle accident reporting and response.
Another challenge I have seen companies trying to address is around monitoring productivity. It's easy when you all sit in an environment where everyone can see each other. How do you manage that when you can't? How do you make sure that people are actually "working from home"?