Had the same issue and did solve it but probably not the way you want. As the Talk upgrade seems wanting to create an index with fields making it to big a size, i went for the solution to somehow get past the upgrade fail and then delete Talk.
Having control over the database, i just logged in and created the index it complains about as a dummy index. Once this was done I logged into the docker container as www-data and did run the ‘occ app:update’ to let it finish whatever update it was doing. Once done, I could log into nextcloud again and there within I delete the Talk plugin.