If there are extensions you use that aren't available on firefox, just contact the developers. Its a bit more complicated if they are still using the mv2 API as that was far more fragmented. with the implementation of mv3, which is required for all new chrome extensions as of january 2023 and will eventually be a mandatory upgrade for older extensions, most extensions going forward will be 90-95% compatible with firefox and safari. Really there are just a few areas the dev would need to do some specific checking/handling for, and then of course getting the builds to the mozilla addons store or safari app store.

A lot of chrome extension devs simply don't realize its much simpler now to support other browsers since that was definitely not the case up until the last year or two. All the browser teams are working with the w3c to have a unified API for extensions and its been a wildly successful effort over the last 5 years.

I build a chrome extension for my job. The only reason we don't have a firefox or safari build yet is purely because none of our customers have asked (its only useful if you pay for our b2b product) but once someone does or we have time to make it happen proactively, its not going to be a big deal.