LNURL is a separate spec from Lightning-proper, even if many/all nodes are using parts of it. Lightning has BOLTs, whereas LNURL has LUDs.

Because LNURL depends on HTTP stuff not the Lightning peer protocol, I'd say that's enough to call it a layer 3 -- you're using it as a separate protocol to make it easier to use and interoperate with lightning, which as a metaphor is like using DNS to make doing things over IP easier

I'd argue things like LNURL and Cashu are layer 3

Initial Block Download for core can take a really long time, especially if your network is slow or hardware isn't that fast (i.e. a Raspberry Pi will complete IBD much slower than a good gaming desktop would). I run a node on an ancient thinkpad for reasons, and that IBD took ~two weeks*! Once Bitcoin Core has synced, the Electrum server will then have to do its own sync where it indexes what core has downloaded.

You can check if Core is actually getting new blocks by looking at the end of the bitcoin-core logs for new lines with "update tip" and new block hashes. I'll guess the log file is at /home/citadel/bitcoin/debug.log for you in Citadel? ('normally' it'd be ~/.bitcoin/debug.log for a DIY off-the-shelf install)

*=I got fed up waiting after a day and swapped the SSD into a desktop, completed IBD there in a day or so, then put it back into the Thinkpad. But it would've taken weeks at the pace it was going.

Work-around might be a pay-per-click ad model (where you'd have to prove a view) rather than pay-per-impressions where yeah, you could just pretend to have looked at it.

PPC still seems pretty easy to fake by getting your client to just fetch in the background, but not sure how that's any different from the current world of ads, except users don't get paid directly for views. How does Brave handle it?