Interesting. I'm surprised it works on any browser.

From what I can see, when www.toonamiaftermath.com loads, it gets a guest id from api.toonamiaftermath.com.

www.toonamiaftermath.com has a well configured SSL chain per https://www.scyscan.com/check-ssl/result/www.toonamiaftermath.com.

However, api.toonamiaftermath.com is missing an intermediary certificate authority per https://www.scyscan.com/check-ssl/result/api.toonamiaftermath.com. Note how there's only 1 record in the chain at the bottom of the page. It should resolve all the way upto ISRG Root X1 or X2 per https://letsencrypt.org/certificates/

This is on the server admin to fix up.

If however, you like to live dangerously, you can force LibreWolf to ignore the error (Keep in mind, this is the browser saying "We can't confirm that this server is who they say they are").

In LibreWolf, open the dev tools panel. (Press F12) Click onto the Network tab. Then load https://www.toonamiaftermath.com/ In the Network panel, you should see one record in red for https://api.toonamiaftermath.com/ trying to load bundle.js with the error NS_ERROR_ blah blah SEC_ERROR_UNKNOWN_ISSUER. Double click that record and it'll open a new tab showing you FF's/LibreWolf's "Warning: Potential Security Risk Ahead" page.
Click on Advanced, then "Accept the Risk and Continue". You might see the service response, you might only see the screen flicker. In any case, reload https://www.toonamiaftermath.com/ and repeat for any subsequent errors. It should challenge for every subdomain/package.
Once done, the site should work for you. You might need to manually click play depending on your other browser settings.

Good luck. You'll need to occasionally re-accept the SSL errors. As mentioned, there's a problem with the trust chain. The site owner likely hasn't set it up correctly, and should be causing it to fail on all browsers. You might have a cached chain somewhere that's allowing it to work on that particular browser.