What happens if you run the below commands:

curl -o deno.zip "https://dl.deno.land/release/$(curl -s https://dl.deno.land/release-latest.txt)/deno-x86_64-unknown-linux-gnu.zip"
unzip deno.zip
./deno -v

First hurdle: I cannot download straight into Stackblitz due to lack of CORS headers from Deno's download site:

Access to fetch at 'https://dl.deno.land/release//deno-x86_64-unknown-linux-gnu.zip' from origin 'https://vitejsvitexr7esd-ly13.w-corp-staticblitz.com' has been blocked by CORS policy: No 'Access-Control-Allow-Origin' header is present on the requested resource. If an opaque response serves your needs, set the request's mode to 'no-cors' to fetch the resource with CORS disabled.

Workaround: I can download to my local computer and then "upload" into Stackblitz env (it stores things in IndexedDB I think so I'm really just "copying" file(s) into web storage on my local computer).

Second hurdle: Stackblitz doesn't support "uploading" files larger than 10MB and deno.zip is ~50MB.

Individual files uploaded to StackBlitz cannot exceed 10MB. Please try again with a smaller file.

Third hurdle: Stackblitz env doesn't have unzip.

Workaround: I can unzip on my local machine, split the deflated deno executable into pieces, "upload" them into the Stackblitz env, and then reconstruct deno from the pieces using cat:

curl -o deno.zip "https://dl.deno.land/release/$(curl -s https://dl.deno.land/release-latest.txt)/deno-x86_64-unknown-linux-gnu.zip"
unzip deno.zip
split -b10m deno # produces files named xaa, xab, ..., xan

# deno-pieces contains the uploaded xa* files
❯ cat deno-pieces/* > deno.zip

Fourth hurdle: The cat command runs for some time but then fails. It does combine some of the files but not all of them. DevTools console reveals the following:

Uncaught (in promise) RangeError: Array buffer allocation failed
    at arrayBufferConstructor_DoNotInitialize (<anonymous>)
    at new Uint8Array (<anonymous>)
    at _0x1353ef.wbg.__wbg_new_8f67e318f15d7254 (filesystem-worker.88b6dd69.js:1:441807)
    at fs_bg.88b6dd69.wasm:0xe5f8
    at fs_bg.88b6dd69.wasm:0x493dc
    at fs_bg.88b6dd69.wasm:0x6f297
    at fs_bg.88b6dd69.wasm:0x6d3e7
    at _0x1e8d0b (filesystem-worker.88b6dd69.js:1:369997)
    at _0x207cad (filesystem-worker.88b6dd69.js:1:369615)

I tried combing pieces one at a time but then Stackblitz froze and reloading the env didn't work (usually the files are still there but Stackblitz must have detected a problem with them and deleted them).

I suspect that Stackblitz has done some special stuff with their web containers to make larger binaries like node, pnpm, yarn, etc. work as inspecting their size on the "filesystem" reveals really tiny, unrealistic sizes:

❯ ls -la /usr/local/bin
total 2
drwxr-xr-x  1   root   root    13  Nov  26  10:56  ./                                              
drwxr-xr-x  1   root   root     2  Nov  26  10:56  ../                                             
-rwxr-xr-x  1   root   root    12  Nov  26  10:56  code*                                           
-rwxr-xr-x  1   root   root  1601  Nov  26  10:56  google-chrome*                                  
-rwxr-xr-x  1   root   root    12  Nov  26  10:56  jq*                                             
-rwxr-xr-x  1   root   root    12  Nov  26  10:56  loadenv*                                        
-rwxr-xr-x  1   root   root    12  Nov  26  10:56  node*                                           
lrwxrwxrwx  1  staff  staff    38  Nov  26  10:56  npm@ -> ../lib/node_modules/npm/bin/npm-cli.js  
lrwxrwxrwx  1  staff  staff    38  Nov  26  10:56  npx@ -> ../lib/node_modules/npm/bin/npx-cli.js  
lrwxrwxrwx  1  staff  staff    37  Nov  26  10:56  pnpm@ -> ../lib/node_modules/pnpm/bin/pnpm.cjs  
lrwxrwxrwx  1  staff  staff    37  Nov  26  10:56  pnpx@ -> ../lib/node_modules/pnpm/bin/pnpx.cjs  
-rwxr-xr-x  1   root   root    12  Nov  26  10:56  python3*                                        
-rwxr-xr-x  1   root   root    12  Nov  26  10:56  wasm*                                           
-rwxr-xr-x  1   root   root    12  Nov  26  10:56  xdg-open*                                       
lrwxrwxrwx  1  staff  staff    37  Nov  26  10:56  yarn@ -> ../lib/node_modules/yarn/dist/yarn.js

Ah, ok. Stackblitz WebContainer is not like docker container. It's not based on linux or any operating system, but it simulates Node.js using browser's JS engine. It can't execute binary executables like deno command. ref https://blog.stackblitz.com/posts/introducing-webcontainers/

I suspect that Stackblitz has done some special stuff with their web containers to make larger binaries like node, pnpm, yarn, etc.

That sounds correct. I think deno doesn't work in stackblitz unless stackblitz team does a similar work about Deno, simulating Deno APIs on browsers.