DevRel here - my formal designation is Developer Relations Engineer. Much of my job comprises of what di's comment [1] speculates as an Evangelist and Advocate combined. I am a part of the hiring panel and describe the work opportunity as follows:

1. a third of the time, you'd be speaking to users (of course, typically developers) to help them understand and integrate with our technology, find solutions and debug issues for them, and make the most out of our stack - this could be thought of as a hybrid between a developer support and a customer success role, where to be able to manage customer success you need to understand a developers problems / persona / psyche.

2. another third of the time, you'll build internal as well as external tooling, and documentation etc around our core offerings - be it SDKs / packages for our APIs, sample / demo apps, quick hacks to use the API from a Google sheet plugin, or dirty dashboards to dig in a particular user metric that is in focus for the month from somewhere across 4 table joins.

3. and the last third would be dedicated to providing proper product and engineering feedback - I feel this to be the most important part of my work, which is to pass on, debate on and participate in well-structured feedback as a consequence of being in direct touch with the customers. This feedback is: a) highly relevant coming directly from the user's pain points but via the value add of a filter from someone who understands the product's proposition and ideology, and b) actionable, as it simply is not "could we provide feature X" or "there is something wrong in module Y" but more like "could we decouple this process from that API call so that users could use feature X in so and so way" and "module Y at step bla is looking for a non-existent entry in the db - most likely cos this certain flow might have triggered it, how quickly can we fix this".

(we also want to expand on community building, events & talks and such, but don't find the right time or motivation to do so, being an early stage startup, although this should not really be an excuse for maybe not putting in the right effort)

I have been in this role formally for only 4 months out of my 6+ working years, but have always felt this coming. Main reasons I attribute to this:

1. I have discovered a wide variety of fickle interests - this area of work covers understanding business(es), being up-to-date on technology (at least the internal frameworks and architecture), relationship building, regulatory knowledge (since I work in a heavily regulated domain), product thinking, and a lot of other things.

2. I suffer from short attention span - not ADHD but it is super simple to distract me, so I haven't been able to find my deep work vibe yet and this job allows for that.

3. I have worked as a developer and didn't feel I was "cut for it" - yes, I said it. Deep tech does not interest me, I've never worked with a front-end JS framework like React or Angular or anything of that sort, and no, I do not aspire to be a data scientist or principal architect someday. All of those are very valuable works and there are a lot more people out there other than me who love it more than I do and certainly do it better than me. So why not leave them to it and I do what I do best - which is to talk to people about - "why" should you use this offering, "what" to do to make it work with your system and not to figure out "how" exactly. Nonetheless, it excites me and I keep reading up on advancements and certain concepts of languages / technologies. Just like I do for a hobby - like board games for example - I play, can teach and sometimes think about them but I'm not a designer or researcher. (Boy, if only we had board-gamer relations as a job, which also paid as well as a tech job...)

Particular disadvantages I feel:

1. I am not a multi tasker - it is not easy at all for me to run parallel threads, which is very much required: partly as a "job hazard" and partly because I'm also not good at time management (refer point 2 above).

To add to this, I have very minimal and unrelated to job Twitter following. I generally write very less on the internet and not even at work (although I want to increase this particular output from myself). And I haven't had a speaking engagement either.
So these are not a part of or prerequisite to the job, but definitely make for a good addition.

[1]: https://news.ycombinator.com/item?id=23908042