Ordering firmware or checksums by post

Sorry if this is the wrong sub forum, I couldn't find any better and I have an old Dell laptop, so...

I'd like to reflash my BIOS with the latest firmware, however I don't necessarily trust my network, including the certificate chain, for a number of reasons. This becomes a real down-the-rabbit-hole type situation when you really think about it seriously, and for that reason I'd like to order the BIOS update on CD-ROM or similar physical media from Dell. I can't find any way of doing that though.

If that is not possible, ordering a hard copy with cryptographic checksums (such as SHA256) directly from Dell would be an equally good alternative.

Is any of these services available?

I know this is an advanced topic and that this is a community support forum, so I'd just like to help people not waste their valuable time giving irrelevant support because of misunderstandings: This is an actual problem, it does not matter what BIOS version I currently have or if I have any issues with the current firmware, etc. Likewise the Coreboot project and similar are not relevant.