Okay, so it looks like the general consensus is that you can't really run a discord RP server and advertise here. There needs to be a more cohesive link between the server and the guild, otherwise the mods will lock the thread. That's a shame but like Harbinger said, the focus should always be on the website and not drawn away onto different apps.
More or less this. Advertising is generally frowned upon, to the extent that it would be breaking a rule. Put simply, you shouldn't recruit players here for something offsite without keeping an active thread. I know there was a Nation RP that did everything related to it on Discord and kept an updated thread by posting a summary of everything that happened every few years.
But yes, using RPG to recruit players without a true connection to the Guild isn't really allowed. Like explained, you need a cohesive link between RP and RPG.