Don’t forget Packet8 business services. They have a virtual PBX, with real extensions, the ability to have the system forward calls to your mobile phone and actual equipment (if you want/need it). We’ve been using them for the past three years successfully with employees all over the U.S.
In practice, most businesses are simply handling this on a case-by-case basis since COVID is a temporary problem. Most home networks can handle the extra load as long as the employee makes sure that other latency-sensitive traffic, like gaming or video streaming, is kept to a minimum during the hours when they need to talk. If some home routers develop problems, IT staff simply build a queue and handle those one at a time. Sometimes they'll be able to access the router remotely with the employee's permission, sometimes they'll have to walk that employee through configuration steps to fix the problem. Sometimes the employee will just have to live with it unless the company springs for a new router or a higher bandwidth tier from the employee's ISP.

Generally speaking, you'll find that the benefits of data network services such as VoIP and SIP are far greater than PRI lines because you have less dedicated hardware and there are more providers to choose from.
23. Howdy, thank you for calling [business name]. Please toddle away your title, quantity, and a short message, and a member of our team will return your name within 24 hours.