SharePoint Online Calendar for Guests

Hello. We have set up external guests to come in and work with us and assigned them to visitor role. On the left side NAV pane, there is a link to Calendar (https://outlook.office365.com/owa/?path=/group/XXXX@XXXXX.com/calendar)

As an internal user to the company, when I click that, it redirects me to OWA calendar and it works fine. As a guest user, (in this case, one that has Office 365 with their own company) they click that and it tries to force them to use their work Outlook account. Is there a better way to keep a calendar within a group set up like this? We are using the Group Calendar webpart which is helpful on the page but I was looking at the Events module. Would that be better to use? Any suggestions on how to address this?  Do they need to just make sure they sign out of their Company Microsoft 365 account and log back in with the user ID they created to be a guest in our system?  Please advise of any strategies here.

What would be BEST would be to somehow have the calendar be quick and easy to access from their phone as well. That is pretty easy task for internal staff but it seems for Guests it would not be easy.