@blinry asks : "Which nerdy DIY kits should I look at for transceivers in the HF range?"
For #hamRadio DIY kits, I'd say anything offered by Hans Summers and his QRP labs https://shop.qrp-labs.com/ is worth a consideration.
Hans is a technically knowledgeable person with cool ideas. I've briefly met him in person at the Friedrichshafen faire a few times and found him a nice person to talk to, too.