The direct download link you used https://keeper.mpdl.mpg.de/f/ec510a79d3ab495eaf67/?dl=1
is a link with redirect.
it seems that Pandoc won't follow redirect and will do the same as in a browser. If I paste the link inside the browser I can this page https://keeper.mpdl.mpg.de/f/ec510a79d3ab495eaf67/?dl=1.png
While the SVG file is correctly downloaded to. It seems Github markdown preview will follow redirect, hence why it works
$ curl -I https://keeper.mpdl.mpg.de/f/ec510a79d3ab495eaf67/?dl=1
HTTP/1.1 302 Found
server: nginx
date: Mon, 06 Mar 2023 10:45:28 GMT
content-type: text/html; charset=utf-8
content-length: 0
location: https://keeper.mpdl.mpg.de/seafhttp/files/2e75692d-e929-4380-93ba-83c01c307c3f/KeeperLogo.svg
vary: Cookie, Accept-Language
content-language: en
set-cookie: sfcsrftoken=CML25R0X8h6r8UasyuBfNcxZCWmKSI8Ty6VUzBLRDcXx7iD95qBciQaPGvYjysGj; expires=Mon, 04 Mar 2024 10:45:28 GMT; Max-Age=31449600; Path=/; SameSite=Lax
strict-transport-security: max-age=31536000; includeSubdomains
set-cookie: SERVERID=app09-keeper.mpdl.mpg.de; path=/
Now if I follow the redirect in the URL provided I correctly get the SVG image
$ curl -I -L https://keeper.mpdl.mpg.de/f/ec510a79d3ab495eaf67/?dl=1
HTTP/1.1 302 Found
server: nginx
date: Mon, 06 Mar 2023 10:49:24 GMT
content-type: text/html; charset=utf-8
content-length: 0
location: https://keeper.mpdl.mpg.de/seafhttp/files/b7bbab02-a94e-4fe2-82a5-7d2cb1e7b24c/KeeperLogo.svg
vary: Cookie, Accept-Language
content-language: en
set-cookie: sfcsrftoken=T2Pg90JHul53lqcSHaoVG7ylphXcQqu3jNYqlrbfRMmO4dYwL50MpawXjqMsis1m; expires=Mon, 04 Mar 2024 10:49:24 GMT; Max-Age=31449600; Path=/; SameSite=Lax
strict-transport-security: max-age=31536000; includeSubdomains
set-cookie: SERVERID=app07-keeper.mpdl.mpg.de; path=/
HTTP/1.1 200 OK
server: nginx
date: Mon, 06 Mar 2023 10:49:24 GMT
content-type: image/svg+xml
content-length: 6202
last-modified: Mon, 06 Mar 2023 10:49:24 GMT
cache-control: max-age=3600
access-control-allow-origin: *
content-security-policy: sandbox
content-disposition: attachment;filename*="utf-8' 'KeeperLogo.svg"
x-content-type-options: nosniff
strict-transport-security: max-age=31536000; includeSubdomains
set-cookie: SERVERID=app09-keeper.mpdl.mpg.de; path=/
cache-control: private
I don't know if and where we could detect 302 redirect and replace the url instead of the user. I'll open an issue about this.