Lots of 404s after Migration

I have used Duplicator to migrate my site from a local webserver (http) to my production site (https with Letsencrypt certificate). The process went smoothly, there were no errors shown, but the production site has multiple (possibly related) problems:

1) I can only see the homepage. Any link to sub-pages I click on returns me a 404.

2) My blog posts and pages are all there in the admin panel, but if I edit one of them and save using the block editor, I get an error message that the response is not JSON.

3) Possibly related to 2) is a problem reported in the admin panel’s site check. There it says that the REST API is not working and returns 404. There are other errors as well, such as action_scheduler_run_queue couldn’t run and module imagick missing. Incredibly, the state of my website is still listed as “good”.

4) One image ist still linked via https://localhost instead of https://www.domain.com – it is used as a background image and probably contained in a stylesheet of my theme as a data-url or something. I can research this further, but the point is, the URL wasn’t updated.

What I manually did after migration was to put the usual SSL config options in wp-config.php, which is needed, because locally I am working with http. And then Wordfence wanted to update some firewall settings including .htaccess, which I let it do. I did afterwards try to restore the old .htaccess, but this did not lead to any of my problems disappearing.

So it appears that something major went wrong, what is your advice for fixing it? I can do a new migration with different options, if need be.