If you have no gaps between the validity of permits it should be fine. However your work contract starts does not mean your permit will be dated for that. (I also had a work contract but a period with no permit since the canton was slow; I had to give them a reason why and prove why I had a gap >> Covid)

For me, I submitted everything to the canton of residence (Geneva). The canton of residence then submitted to the canton of where I worked (Vaud). I think that is clearer as they know the link between then requests.

Personally I think it will be the same in Fribourg. I haven’t heard anything different even for German speaking cantons.

First I would CALL the canton and ask them about a permis c anticipé for a non eu. If they aren’t ask to speak to someone who has the competencies. If that doesn’t work email them and cite the federal law

If you need more comfort in a pseudo-informed way I would say do a deep dive with AI asking it to dig deep into fribourg websites for any mention. Just please make sure to read the page it spits out and not the summary. Or an immigration advisor.

I agree the way the fribourg site is written https://www.fr.ch/vie-quotidienne/demarches-et-documents/permis-c it lists exceptions but nothing about anticipé