Not many Office 365 users choose OWA as their mobile client, but those who do will soon be forced to use the new OWA because Microsoft is removing the toggle to allow people to switch between the old and new versions in February, just like they did for workstation versions last July. The new OWA is a fine client, but its usefulness on mobile browsers is not as good as the functionality offered in Mobile Outlook, which continues to be our choice as the best mobile Office 365 email client.
https://office365itpros.com/2020/01/28/new-owa-default-mobile-browsers/
