How do I sign into a WiFi network if the website doesn't automatically pop up???

Pizza Hut Guest requires this, McDonalds Free WiFi does too, and more specifically the one that is ******* me off is the Anytime Fitness Guest WiFi, which first requires a password, and then requires the website login. On my iPhone it's pretty straightforward, it always pops up. But on my MacBook Pro 2020 I never ever get that pop up so I just end up never using my MacBook outside of my home...

But now I am done. I just want to be able to use my MacBook on WiFi literally anywhere else. Somebody please help me out, I seriously have no clue how to force the website to pop up when the WiFi isn't connected to the internet. I'm not going to go to some third-party website about this because I know I will end up messing up my MacBook on accident.