Loader version and type (918+/3615xs/3617xs): Jun's Loader v1.03b - DS3615xs
DSM version in use: DSM 6.2.1-23824 update 4
Using custom modules/ramdisk: NO
Hardware details: HP Elite 8200, Intel Core i5, integrated NIC Intel 82579LM
Prerequisites:
Computer needs to be booted in Legacy BIOS mode for network to work. However HP Elite 8200 UEFI BIOS refused to boot loader in Legacy mode, only EFI.
Booting EFI mode makes that network is not working for Jun's Loader 1.03b.
How I solved the boot issue? Loader's USB key partition table has Protected partition table. And looks like HP's UEFI BIOS for mentioned model has issues booting in Legacy mode in that situation.
I converted USB key's partition table to Hybrid partition table. That helped BIOS to see MBR partitions and boot in Legacy mode.
For conversion I used 'gdisk' tool in linux/macOS. I selected all three USB key's partitions to be part of MBR partition table, whereas I flagged first (EFI) partition as bootable for Legacy boot to work correctly.
To make Legacy boot mandatory I could disable all UEFI boot options in BIOS. However I rather renamed EFI folder name on first USB key partition to something else. That way Legacy boot became the only option for that USB key.