Note, since MS Teams has been integrated with 'Single Sign On', no sign up to MS Teams is required.
The current platform choice for online classrooms if dial-in is not required is MS Teams. The primary reason is it satisfies the following critical criteria
Identity verification through IITB LDAP email: MS Teams' IIT Bombay offering is uses 'single sign-on' to validate user identity against IIT Bombay's Single Sign-On server. No sign up required, and identity spoofing will not be easy.
A classroom (an MS Team) can then be created by signing up all enrolled LDAP IDs to the classroom. (Note, rollnumbers of students may not be their LDAP IDs)
The online meeting started will then be automatically available only to enrolled students.
Any prank is traceable to this ID. 'Anonymous' joining is not enabled by default (but non-IITB emails can still be invited to such a meeting).
A meeting link can still be sent to someone who can join without having an Microsoft account, nor any MS Teams client/ app.
Other popular platforms like Zoom have no such arrangement with IITB at the moment, and identity spoofing is trivial. Other platforms are still a bit experimental. Free Zoom accounts also have participant and time limits. Paid Zoom has not had competitive pricing.
MS Teams also is fairly feature -rich, and wins on many other counts. See this comparison matrix for details.
The current platform choice for online classrooms if dial-in is required is Webex, for the simple reason that it is the only platform which has India domestic dial-in numbers. If any of your students is having trouble connecting through any meeting software/app, the Instructor must switch to using Webex.