Thunderbird can be used with any e-mail address. It doesn't matter whether a person uses any version of MS Office 365 or not. Just go through the Mail Account Setup in the program.

Your online version of Office 365 will prompt you to use Outlook webmail. Just like everything else in online Office 365, everything is done on the server, and none of the programs are actually installed on the computer.

Thunderbird is a program you actually install and run on the computer (runs "locally"). So your computer does the work, not some Microsoft server.

Thunderbird connects with Office365 accounts using the IMAP protocol. This synchronizes a local copy of your mail folders with the copy on the server. Thunderbird is a bit of a second-class citizen for Microsoft mail services because (as far as I know) Microsoft doesn't provide a way to sync calendar entries or contacts for non-Microsoft mail clients.

To check whether you can use IMAP with your Office365 mailbox, you could check your Mail Options. In particular, look for a POP and IMAP section as shown in the attached screenshot.

https://outlook.office365.com/owa/?path=/options/mail

If you have instructions for using IMAP in that section, I assume (!) you can use it.