Honestly, a policy of "no free-of-charge software installed on workstations except FOSS" might improve security a bit and probably without doing all that much damage to the day-to-day workings of the company.

For that matter, if my employer instituted a policy of "no software except FOSS", my own particular job probably would be a surprisingly small adjustment. As long as they were willing to do the work to set up infrastructure and/or let us switch to FOSS alternatives that require third-party server providers as necessary. About all I can think of that's installed on my work machine that's proprietary is:

• Zoom
• A paid corporate VPN client
• A random program that I use to authenticate to Kubernetes clusters in use where I work (so I can use Kubectl)
• Chrome
• The Client Management software my company uses (the software they use to remotely administrate the company-provided machines -- force install shit without telling you, spy on you, nag people who have computers that aren't actually used to return them, wipe your computer if you report it stolen, etc)
• And, of course, bios, proprietary firmware blobs, etc

Beyond that, I honestly can't think specifically of anything else proprietary installed on my work machine. My personal computers have far less proprietary software installed than the above list.