To be more precise the last time I did this I had to: - Adjust cookie SameSite attribute (cookies didn't work properly otherwise) - Migrate back from MV3 to MV2 (Safari DevTools are really bad for MV3 for some reason and there were also other issues that didn't appear in MV2) - Adjust JS and CSS (some newer techniques were simply not supported in Safari)

Firefox didn't have any of those issues. On top of that, there's much more resources available online than there is for Safari - though, to be fair, it's mostly because its support for WebExtensions is newer and there aren't as many extensions for Safari. But, when you do find some resources you have to verify whether they're actually on the most recent standard - Web Extensions - since Safari supported multiple over the years, that have nothing to do with WE, and are very similarly named: Safari Extensions, Safari App Extensions, Safari Web Extensions