How can I pass around filenames with special characters in them in Windows?

I want to get the MD5 checksum of a file called "🔥.txt". This works fine in Cygwin:

$ md5sum 🔥.txtd41d8cd98f00b204e9800998ecf8427e 🔥.txt$ openssl dgst -md5 🔥.txtMD5(🔥.txt)= d41d8cd98f00b204e9800998ecf8427e

But outside of it, I cannot:

$ md5sum 🔥.txtmd5sum: can't open '.\??.txt': Invalid argument$ openssl dgst -md5 🔥.txt.\??.txt: Invalid argument6C2A0100:error:8000007B:system library:file_ctrl:no protocol option:crypto\bio\bss_file.c:297:calling fopen(.\??.txt, rb)6C2A0100:error:10080002:BIO routines:file_ctrl:system lib:crypto\bio\bss_file.c:300:$ busybox md5sum 🔥.txtsum: can't open '.\??.txt': Invalid argument

I thought maybe I could use the 8.3 path name, but dir /-n shows that the 8.3 name has the emoji in it too.

I've been trying to find if there's some alternative to coreutils sum that might be able to handle this but I can't see anything. I can't find anything in the Windows documentation about converting the filenames into something readable, either. And this is causing me a lot of headaches because rclone relies on md5sum working to transfer files, so right now I can't transfer any files to or from Windows machines.

What can I do?