Hi,
this infamous error returned with T4 Framework 2.2.0 on our production site running Jomla 3.10.9.
It did not occur on our test site that was already upgraded to Joomla 4.1.4 one week ago. I rolled back T4 Framework to 2.1.9 on our production site and everything is fine again.
Production site running Joomla 3.10.9 with rolled back T4 Framework 2.1.9: https://www.ulc-moedling.at/
Update: T4 Framework also breaks frontend article creation editor with Joomla 3.9.10. It just displays "Content" tab with 2.2.0. After rolling back to 2.1.9 it shows all four tabs again (Images & Links, Publish, Language & Metadata).