Resizable BAR is reliant on having a dedicated video card, not supported in an APU, an APU is already talking faster then ResizableBAR.
Example I see you have a 3080 like myself, but you must have it connected thru the M.2 slot. And to the best of my knowledge ResizableBAR isn't going to be supported thru the M.2 vs an actual PCIe x16 port/slot. I personally don't see a bios update for that ability coming any time soon from any manufacturer personally.
A big point to why I don't see it happening, ResizableBAR REQUIRES a chipset for it to be PUT ON TO the mobo.
AMD: 500 series chipset required (AMD users are a bit more limited), so as long as the 5000 series from MinisForum have the needed chipset then they could BIOS update this issue.
Intel: (Some older Intel motherboards received BIOS updates to enable Resizable BAR, but support varies by motherboard vendor.)
NOTE: This technology is integrated within the PCI Express 3.0 standard. But doesn't mean it's on the MINI MOBOs.