UPDATE:
We have delayed further rollout of Thunderbird 102.7.0 while a suitable patch is implemented to resolve a critical OAuth issue

If your client was already upgraded to 102.7.0 and you wish to use a previous version for the time being, please install and launch an older version, for example, 102.6. Thunderbird should automatically detect your existing profile.

However, you can launch the Profile Manager if needed by following these instructions: https://support.mozilla.org/en-US/kb/profile-manager-create-and-remove-thunderbird-profiles#w_starting-the-profile-manager