Sales Development Representative jobs for B2B SAAS
That role does not exist (and never existed). SAAS companies as we all know are cloud based softwares and SAAS companies always do their marketing through digital media advertising & digital media promotions (including affiliate marketing networks) and they never hire sales development representatives.
Sale development representatives are nowadays hired by companies into actual brick & mortar based businesses.
So if you are interested to market an SAAS service, then become an affiliate marketer (or / and referral based marketer) for one or more of them : most of them manage their affiliate marketing part through affiliate marketing platforms (networks).
And pertaining to the above, in-depth knowledge SAAS is absolutely not needed. What will be needed is digital marketing skills pertaining to the digital marketing platform(s) you would use as an affiliate marketer (example skills pertaining to Google Ads, Facebook Ads, Reddit, Quora, YouTube, etc, etc, etc).
Nowadays, when it comes to freelance remote earning, it boils down basically to skills that revolve around digital marketing, such as content writing, SEO, usage of ad platforms, building landing pages, creating videos, etc, etc. And no one knows all these skills. People usually start by trying to specialize in 1 of them and then build further from there, sometimes on an ongoing basis also outsourcing certain tasks. For example a content creator has a website, but he may outsource the SEO part from time to time as per need.