One challenge is that in many places (especially the most profitable areas), the last mile is already built out. So by saying "municipally owned fiber" you mean laying new pipes to replace existing pipes (significant material cost) or trying to wrestle control of the existing pipes away from large ISPs (significant political cost). A small to medium sized city cannot just tell AT&T "give me your fiber", and it often lacks the capital to put down new fiber. Even if a small project could be completed, the dominant ISP in the area would simply lower their prices enough to make the project uneconomical, thus preventing the project from recouping its costs and staining the idea of publicly owned internet infrastructure.

Then maybe more thought should be given to how the dominant ISP's as well as other anti-competitive business practices have put the local municipalities into a position where they 1) don't have the cash to lay down their own pipes 2)are put in a position where blatant anti-competitive behavior like strangling newly laid pipes would not be adjudicated fairly. A two prong approach of subsidizing local pipes and pressuring existing fiber to behavior fairly.

I'm not sure that's required, at least for urban areas cables are not that expensive. The problem might be deliberate anti-competitive collusion between the major ISPs.

More generally: government owned. i.e. could be provincial, federal, etc. Like how water pipes and electricity already are (in many places).