First post on the forum so be gentle.
TL;DR: The Spanish company Nueva Pescanova is planning to farm octopus and begin selling it on the market in 2023. They intend to sell 3,000 tons of farmed octopus per year, which amounts to several hundred thousand octopuses. This is concerning given that octopuses are highly intelligent animals; there are no released standards for how the octopuses are going to be kept and raised, nor for how they will be slaughtered. There doesn't seem to be much in the way of coordinated action against this yet.
Link to the article: https://www.bbc.com/news/science-environment-59667645
Eurogroup for Animals (a European Union lobby group representing other animal advocacy organizations) has encouraged EU citizens to submit feedback in the EU's animal welfare legislative review - though it is better to make a submission on behalf of an organization rather than as an individual citizen.
In addition to answering the multiple choice/tick-box format questionnaire prepared by the European Commission (which addresses cage-free hens and fish welfare among other issues), one can add in a request to ban/restrict such cephalopod farming under the section "Is there any other comment you would like to add?"
Deadline: 21st January 2022 (Midnight Brussels time)
Eurogroup also has a report on "Decapod Crustaceans and Cephalopod Molluscs in EU Animal Welfare Legislation" and include the legal basis for banning such practices on pages 13& 14 of their white paper. I have not independently researched how strong this legal argument is.
I also think much of what Kieran wrote above sounds right.