After an unrelated disaster (see this post) I had to reflash my phone back to stock Android (in my case SM-G965F_VNZ_G965FXXUHFVG4_fac.zip), and then install latest /e/OS (2.3-t-20240820427106-dev-starlte).
After this update tethering is now working - I’m writing this post via my tethered phone.
So some good came out of a bad situation 