As the current user of an FP3 that’s slowly starting to show ‘weird behaviour’ I’d be rather hesitant to buy a new one if repair options are virtually unavailable to you. Apart from that, I can’t add anything useful to the discussion
However - I just want to mention how much I love to see someone else who seems to value workers’ rights over modularity. I know those go together quite closely, but lately many Fairphone users seem to focus only on repairability and material sustainability, rather than on the people actually making the materials and assembling the phones!
…also, I’m afraid very few other electronics manufacturer’s take workers’ rights as seriously so I don’t know of proper alternatives to Fairphone, except buying secondhand as you already do.