This one is hard for me too test as I have a PC. I have tested with Chrome, FireFox and Edge and all seem to remember passwords fine on the Geeklog.net login page (with the recaptcha enabled).
ReCaptcha may send a request not save passwords. You can disable these type of requests in Safari apparently. Quoted from Cnet:
To do this, go to the Passwords section of Safari's preferences, where you will see a checkbox at the bottom of the window which says "Allow AutoFill even for websites that request passwords not be saved." Toggle this setting, and you should now be able to save your site's password.
One of the Geeklog Core Developers.