See this comment;
I think all their pods are by default sized for ATX boards. My Q30 circa 2014 was also. Their default motherboard at the moment on the enterprise side is an X11SPL. I don’t think a stretch version for HL is anywhere in the works (they are focusing on smaller stuff, not larger). As indicated by the comment though, they should have the ability to make stretch versions of chassis, at least the Q30, probably the AV15 and F8X1, perhaps even the HL15. Unfortunately, it’s not click-and-ship; you’ll need to speak to sales and get a quote.
Your Gigabyte board should fit the HL15. The front position of the 24-pin ATX power might be tight, but I think it would be ok. If you want to use the SATA connectors, you’d need to temporarily shift/remove the mid case fans to plug and unplug the cables. Not at all difficult; just four screws. The Asus board won’t fit.
Are you looking to rack mount, or use the case as a tower? If EEB form factor is a must as well as support for full height graphics cards, and you can’t stomach the 45Drives quote, you may need to look at a used Supermicro case like the CSE-846. Although they come with their own quirks. There are also 2U (CSE-826) and 3U (CSE-836) versions with less drive bays, but you’d be limited to either low-profile cards or passively cooled server-targeted cards like the A4000 that are no taller than a full height PCIe slot. Most of the consumer GPUs have fans and shrouds that make them taller than 3U.