I wanted to create a concentration-type spell that basically produces a continuous explosion around you as long as you hold down the button.

No problems whatsoever from the technical standpoint: spell fires, spell continually blasts, spell kills people, spell drains my mana.

However, I wanted it to be a "ritual" spell, that is, I wanted the character to do the funky chicken dance that is attached to all Master-type spells before the actual cast. I added "RitualSpell" keyword to the magic effect, set the Cast Time to the safe 3 seconds, and gave it a go. My character waved his hands through the initial windup, and then abruptly stopped, and the spell never went off.

There is a grand total of one more concentration-type ritual spell, the Lightning Storm (master destruction), and it works just fine, but it uses "Target" delivery method (unlike mine that uses "Self"). Is the "ritual spell" animation just buggered and does not work for "Self" delivery method?

It's very possible this is the case. I'm wanting to do the same, so I'm still playing around with it. I'll have to look at the lightingstorm spell and see how it works. There might be a way around this issue...

This is quite annoying. It seems what you stated is true--for some reason, you are not able to cast a ritual concentration spell on yourself.

I'm trying to think of workarounds using aimed, but they're really hacky methods that I'm not too fond of.

make an aimed spell with an effect that does nothing/nearly nothing
give the player an ability that checks to see if the spell is being cast and cast the actual spell on the player

it'll still have the target animation though

Yeah, I'd thought of something like that, but that really doesn't work for what I'm trying to do.

Truthfully, I just want to play the ritualspell animation while casting a spell. However, I need a script to start the exact moment that the player finishes the animation for the ritual spell (IE: Not when they release their mouse button.) Then, Once they DO release their mouse button, I need to immediately run another script.

A self cast concentration spell allows me to do exactly as I've described. The script runs once when the spell starts, and once when the spell finishes. However, if I change that to a ritualspell, it stops working entirely due to the bug the OP posted out. If I make the concentration spell aimed instead of self cast, then the script on the spell won't run until it hits something, and it will run once on everyone the spell hits, while also running the "finishing code" whenever I stop hitting them with the spell--Somethign I do not want. This is why I called the workarounds "hacky", because they would result in such issues.