I noticed the Umbraco logo here and the one in header are bitmap graphic:
https://forum.umbraco.com/about
Depending on screen resolution it may be a bit unsharp.
I searched on the topic and it seems the logo is used in emails, where SVG isn’t well supported Can I email… Search (I know, it’s 2025 ), but it seems there should be a separate logo setting:
SVG Logo Upload Support? - #9 by Amethi - UX - Discourse Meta
The site logo Discourse use itself in the link above is SVG, so I guess it should be possible