Microsoft, OATH hardware tokens for Azure MFA
Microsoft, Passwordless authentication options for Azure Active Directory
US Government General Services Administration, DotGov
WebUntis - Online timetable planning for schools
UserLock by ISDesicions - 2FA & Access Management for Windows Active Directory
HelloID from TOOLS4EVER, a Cloud-based Single Sign-On IDaaS Software
https://www.365dude.nl/2019/05/10/Hardware-Tokens-without-AADPremium/
http://www.365dude.nl/2019/04/30/using-oath-tokens-with-azure-mfa
https://randsnet.blogspot.com/2018/11/multifactor-authentication-to-microsoft.html
https://www.nblabs.net/2019/03/03/azure-mfa-hard-token-and-multi-device-support/
https://c7solutions.com/2019/01/token2-hardware-oauth-tokens-and-azure-ad-access
https://c7solutions.com/2019/03/hardware-tokens-for-office-365-and-azure-ad-services-without-azure-ad-p1-licences
https://osddeployment.dk/2018/11/03/how-to-use-oath-hardware-tokens-with-azuread-for-mfa/
https://blog.o365mvp.com/2019/01/29/azure-ad-mfa-by-token2/ [in Japanese/ 日本人]
https://www.wpninjas.ch/2020/06/use-oath-totp-token-with-azure-mfa/
https://regroove.ca/stellark/2020/11/06/azure-mfa-using-hardware-tokens/