So, my wife and I, both Non-EU were given L permits this summer (mine for family reunification, "work requires authorization"). I work in the cultural sector as a freelancer. I explained to the authorities when applying for family reunification and canton change that I need to have an authorization to work for multiple employers, as in my field there is no such thing as a full-time job. It's mostly a mix of very part-time jobs and/or full-time short-term contracts of a few days. This obviously doesn't quite fit in the "boxes" of the system, so they still gave me the permit "without gainful activity/activity subject to authorization".
But when asking about the process to then get authorization to work, I received contradictory information. In Valais, the migration authority said that when I have my first work contract signed, I merely need to declare it to the commune and ask that they reissue my L permit as "with gainful activity", and that I thereafter would have a right to be employed without further authorization, including by other employers for other projects. There seems to be no work permit application required, only I need to bring my work contract and declare it.
I found that surprising, as colleagues of mine in the same situation but in different cantons were very clearly told that they had no right to work, and that each and every employer they work with had to get a work permit to hire them. The work authorities in Valais were somewhat ambiguous, saying that they would have to review and approve the work contracts, at least for work in the canton, but they also said that "it's up to the migration authorities". I asked the Basel Stadt Amt für Wirtschaft und Arbeit, as a lot of my work is still in Basel where I lived before, and that is where Basel-based employers would have to apply for permits for me if it is indeed required. They said yes employers absolutely have to apply for permits everytime, in the canton they are based in.
So I'm puzzled at whose advice to follow, my canton's migration authorities or the work authorities in the cantons where I will get a lot of my work...
Does the work permit have anything to do with taxation and social contributions, or is it only a matter for immigration?
(side anecdote: the Basel Amt guy was flabbergasted by the fact that we got L permits rather than B despite my wife having a full-time permanent job with an indeterminate duration contract. He wasn't aware before I told him that certain cantons explicitly require having a L permit for 24 months before getting a B. He laughed pretty hard, and was somewhat outraged, saying that the federal immigration law is clear that that is not what L permits are supposed to be for, and that those cantons are "making up silly rules that don't align with the law".)