A notebook PC will be required by you. This is essential as all of the files the you will likely need will be digital. If that is the case, then a computer is essential. Since you will not be able to bring your desktop to work with you, a notebook PC will be essential. The OS? can be anything with exception of Chrome OS. This is because Chrome OS will not be able to support interacting with LAN servers, nor support the document format used. You will be able to use any updated version of Linux, MacOS, or Windows. I will not fault you for your choice of OS as long as you are familiar with it, and can use it in a manner you are comfortable with.
If you do not have a notebook PC, and you need one for work, you can acquire a Technology Allowance which will give you $1,500 for a notebook PC. You would have a decent amount of options available to you, and this will be a choice you would have to make. If you are not familiar with any OS, then I would recommend a Linux or Mac PC. In my experience, Windows have problems, and probably should not really be trusted.
If you decide on a MacOS PC, you can acquire the Apple MacBook Neo which is $700 for the version you should consider. With a $50 sales tax, you would be up to $750 which is $750 less than your technology allowance. You may consider using the rest of the money to apply to an iPhone 17e if you also need a smartphone. While these 2 items will not exceed your technology allowance, you can still choose to spend some of your money to acquire a better solution. If you already have a smartphone you are happy with, then you do not need to upgrade. You would just need the SIP? client to install on your phone. While there might be a free option available, the really good ones will be more expensive. An office receptionists does not require a smartphone, but I will assume that they have one nonetheless. Instead, they will answer incoming calls with a SIP phone.