Seems that the most efficient way to find a free software job is by contributing to free software projects and doing a good job at it e.g. i contribute to free software on semi-regular bases and i get job offers pretty much multiple times a week.
The other way that i saw is people asking in free software oriented communities e.g. libreplanet mailing lists.
Lot of employers are also interested in hiring people for apprenticeship as in general those are much easier to work with then senior developer and they cost less e.g. i taught a rustlang to a student and he started contributing to rustlang projects and got fulltime hired to work on rustlang for it.
but again the most efficient way to get hired by e.g. prusa to work on a prusa-slicer is by submitting quality contributions to prusa-slicer and prusa will most likely want to hire you after that.
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Also consider working as a contractor as those usually earn money more efficiently through addressing bug bounties (e.g. https://github.com/go-gitea/gitea/issues/14562 i abandoned the work as it would need too much work for my usecase) and getting hired to fix problems.
