Multiple owa Access

Hi,
I have 3 domain (let's call a.com, b.com, c.com) on Exchange Server 2016 and want to create multiple owa access for these different domain users. (like mail.a.com/owa, mail.b.com/owa, mail.c.com/owa)
Currently my default owa address is https://servername/owa. I tried the following articles and created iis sites and virtual directories for each one. I can't connect any of these owa addresses I mentioned above.
https://johnyassa.wordpress.com/2012/06/07/publish-multiple-owa-ecp-virtual-directories-on-one-exchange-2010-cas-server/
https://techcommunity.microsoft.com/t5/exchange-team-blog/configuring-multiple-owa-ecp-virtual-directories-on-the-exchange/ba-p/611217
How can I configure correctly this setup?
Thanks.