Try lowering the random_page_cost value; this is the performance cost query planner uses for random reads, which is usually too high if you're using an SSD where random reads are cheap (on disks it's expensive). Just setting it to 1 works well in my case.

This solves many "it does a slow seq scan even though there's an index"-cases.

https://postgresqlco.nf/doc/en/param/random_page_cost/

There are some other query planner knobs you can tune as well; the https://postgresqlco.nf site is pretty good.