Turns out, you have to prefix the private key with "p2wpkh:", or else it imports it as a legacy key, and generates a completely different public hash.
If you just paste the raw key, Electrum uses a legacy format, and none of the transactions show up for that private key. Adding the "p2wpkh:" prefix to the key makes the transactions show up, but I realized that well after someone else claimed it.
I don't know if this is an Electrum thing, if this is considered general knowledge now for those who regularly use BTC, or if it's a quirk of how BTC has evolved.
Pasted the private key into the email address field on the Wufoo signup page, and the validator helpfully told me my "email" was invalid, with the whole key included.
Actually even worse it's neither an OS level or dom level item custom chrome rendering layer.
And yeah, it's a CTF, gotta hold onto issues until the flag redemption is back up.
Real patch is a chromium update (like a week of work) so imma avoid that until needed.