I am in a similar boat, from what I can tell you can disable the Gemini app here[1] but if you want to disable it in Gmail and Drive you need to have an enterprise plan then you can disable it here [2]
[1] https://admin.google.com/ac/managedsettings/47208553126 [2] https://admin.google.com/ac/managedsettings/793154499678
Wow, thank you. This was buried deep (not an accident of course).
"Pay us more money, or be forced into using our feature" is a new sales tactic.