Is the Army giving everyone a personal device to run Threema on? That's why people use WhatsApp - because people already have it on their phones. If the Army wants people to install a special app people are likely to ask them to provide the device.
I don’t think anyone has been expecting a paid-for device for the past two years just because to work you have to install Zoom, even in the US.
Most employees have to buy their own work tech devices outside of the US?
There are companies that provide some budget for work equipment, but unless it is mandatory by law the budget and quality of equipment varies a lot, from good to terrible or none.
We (big employer in the UK) can order paid-for devices on the corporate purchasing system. It works out best for everyone: they can control the device, I can turn it off at the end of the day, and nobody has to see my reaction when they say "oh yeah, now we can remote-brick your personal phone."
When WFH became more widespread at the office in 2020, the local mgmt team told everyone to enter all sorts of information into a spreadsheet like their IMEI number, etc. Then people discovered after the fact that their personal devices were now managed devices. Cue surprised faces.
MDM rejects bootloader unlocked devices, so even if you have extra devices you might not be able to use them because of that or the OS version being too low to please them. A good alternative if available, is to use Citrix Receiver instead, it doesn't require MDM and doesn't require permissions. It does require an RSA keyfob.