Try things like "Play By Forum" or "Play By Board" instead of their acronyms. 

Also, I've found that many of these sites advertise with each other (unlike the Guild, their ecosystem is pretty open) and you can usually use it to site-hop a few links to find something more appropriate if the first result isn't appealing. 

Try also searching for a specific fandom, like "Star Wars roleplay" or "Harry Potter roleplay." That will likely lead you to these boards. 

Finally, if using Google, be sure to add "-site:roleplayerguild.com" to the end of your search terms so that RPG doesn't come up in your results. You can add more pages to this ("-site:roleplayerguild.com,google.com") if lots of results are popping up for them.