Professional voicemails are important, because they’re an extension of your personal brand, reflecting what level of professionalism you offer. Use these voicemail greetings for work or personal cell phone messages for your specific needs. You can choose a voice that will best suit your business and will deliver a warm and professional voice message. Your callers don’t want to hear a cold and indifferent machine voice. The information you want to put in your voicemail should be succinct enough for your callers to get every bit of information they need. Leave the relevant information in a clear and precise manner. Professional voicemail greetings for work should be informative. The first message the customer hears should have the company’s name so they can be sure they’ve reached the right number. Be courteous and informative. This could be their first point of contact, and you want it to be enjoyable. You may also like 30 Best Wishes and Congratulations for New Business Adventures If you’re going to make your voicemail message humorous in some way, it should be tasteful and aligned to your brand. It shouldn’t get in the way of giving customers enough information when they call. Your voicemail greetings for work should be welcoming and friendly but not too informal. Customers want to feel confident that they’ve contacted a professional, that the company values their call, and they have made the right choice. So be friendly but not too nonchalant. Your voicemail greeting should be clear, concise and to-the-point. You don’t have to put your clients through a sales pitch when they are trying to just get some information.
That rich feature fabric can change radically between vendors, however. For example, RingCentral's softphone offers a long list of app integrations and features, including not just collaboration platforms, but bi-directional email and scheduling among other things. Line2's softphone client, on the other hand, is specifically designed to be simple so users can pick it up quickly, and it does this by mostly mirroring the buttons you'd find on a standard desktop handset. Two ends of the spectrum, but that means you need to be very careful when testing these apps to make sure you're getting not only what you need but in the right way for how your company does work.

https://www.onsip.com/voip-resources/smb-tips/business-voicemail-greetings-5-sample-scripts
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.