What about these software solutions:
- Authy: Free software, compatible also with Mac. Not open source and it requires a phone number to validate the user. https://eur02.safelinks.protection.outlook.com/?url=https%3A%2F%2Fauthy.com%2F&data=04%7C01%7Cchristif%40unhcr.org%7Ccf41b2c2b6f640d669f108d88a2b8273%7Ce5c37981666441348a0c6543d2af80be%7C0%7C0%7C637411266758082809%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C1000&sdata=SnX539hihqR663NG2rHmm%2FxZambSo7ODans3wPunLzY%3D&reserved=0
- Winauthy. Opensource, very easy to use. https://eur02.safelinks.protection.outlook.com/?url=https%3A%2F%2Fgithub.com%2Fwinauth%2Fwinauth&data=04%7C01%7Cchristif%40unhcr.org%7Ccf41b2c2b6f640d669f108d88a2b8273%7Ce5c37981666441348a0c6543d2af80be%7C0%7C0%7C637411266758092803%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C1000&sdata=MchdK70Qut8b8z7D3YqsKpVakA0OUlNJSdbO6NhDRfk%3D&reserved=0
- 2 Factor authenticator. Available in the Microsoft store, it can be made available in the company portal. https://eur02.safelinks.protection.outlook.com/?url=https%3A%2F%2Fwww.microsoft.com%2Fen-us%2Fp%2F2-factor-authenticator%2F9nblggh5k7jn%3Factivetab%3Dpivot%3Aoverviewtab%23&data=04%7C01%7Cchristif%40unhcr.org%7Ccf41b2c2b6f640d669f108d88a2b8273%7Ce5c37981666441348a0c6543d2af80be%7C0%7C0%7C637411266758092803%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C1000&sdata=lQ1dMhqvMd34Ria2POLQfQwptAUwdy9Jk0ihe43rfhI%3D&reserved=0
- Oracle mobile authenticator on Microsoft store, it can be made available in the company portal.
https://www.microsoft.com/it-it/p/oracle-mobile-authenticator/9nblggh4nsh8?activetab=pivot:overviewtab
At the end you cannot stop users to use them. Winauthy for example it's a portable one.
Thanks
Christian