If you use event content types in your Plone site, you might be interested in the development of collective/icalendar to support zoneinfo
as the replacement for pytz
for Python 3.9+. This project recently received funding as a critical project. Plone uses this library to generate .ical files.
Please consider following the project on GitHub and reviewing pull requests.
The work @niccokunzmann is pouring into icalendar is impressive, and deserves our support. It is critical toward the PLIP [DRAFT] PLIP #5629: Enhance timezone support in UI for `plone.app.event` based types · Issue #5629 · plone/volto · GitHub.