Searching for a sim-card router

In theory that should be precluded by the EU net neutrality provisions, no? See e.g.:

https://www.berec.europa.eu/en/all-you-need-to-know-about-net-neutrality-rules-in-the-eu

And:

Notwithstanding Brexit in the UK the regulator Ofcom supposedly enforces net neutrality, albeit in reality they seem a little weak and lazy - see here:

In the UK I think no mobile operator tries to prevent use of phone data sim in router, albeit O2 included a clause to this effect in their 'fair use' charter.

But still I imagine a consumer could purchase O2 phone data sim, then try it in router and if it does not work then return it within the 14 day cooling off period. If it did work but then O2 complained, then one could cite the net neutrality provisions, refer to regulator, and request that the complaint is dropped, or request cancellation of contract and then switch to one of the other suppliers.