TFTP and ISO boot fails on old Z77X-UD3H, Atheros RT8151

[Koli0842]

[x]: This bug persists when memory is increased beyond 8GB.

Describe the bug
I have an old ~2012 Gigabyte Z77X-UD3H motherboard with Atheros RT8151 gigabit NIC, that has UEFI and supports PXE boot. When booting I get the NBP file downloaded succesfully, then iPXE initialising devices..
where my system hangs. There is also autoexec.ipxe not found, but from what I've gathered that's not an issue. I can also see messages suggesting a timeout in the logs:
2025-06-03 22:37:43 err dnsmasq-tftp[32]: error 8 User aborted the transfer received from 192.168.2.58
I have tried all x86 files, both efi and kpxe to much of the same results.
I have tried the bootable ISO on a USB stick option, where I get to "Available devices..", get prompted for failsafe menu for a fraction of a second, then get a generic BIOS message of no bootable device detected, etc.

To Reproduce
Steps to reproduce the behavior:
Would probably require my set of hardware, as the hosted instance works fine on other machines

Expected behavior
A working menu like on my other PCs

Additional context
I host Netboot.xyz from TrueNAS, and use Ubiquiti's DHCP settings to point clients to a file. I have modern PCs that boot from PXE fine and work well. I encountered #1198 where there was an extra character at the end of the filename and was able to get past that with a workaround. I work in tech, I know a fair bit of things, but I am clueless about what makes PXE tick. I am clueless here.