Just updated to 4.33.19759 (5240404f16, 7/20/22) on my Libra 2, and I can't make pinch to change font size work. There is also no "pinch" option in Reading Settings (either from the main menu, or when reading a kePub book) as described in the release notes for this firmware version. Pinch does work with PDFs.
I saw a thread on
Reddit saying that Kobo support indicated that the "pinch" feature was supported on Libra 2 only for PDFs. I haven't contacted Kobo support myself yet, but am wondering if anyone here has any other info, or can confirm / deny this working on a Libra 2 for ePubs (not just PDFs).