There’s still one painful workaround to get SVGs into Google Slides! I actually posted it in that bug thread at Google and then ended up with people attacking me like I was on the team and claiming the workaround is good enough. Anyway, here’s how to do it:

Download Inkscape and then convert your SVG to EMF (some PowerPoint vector format I think).

/Applications/Inkscape.app/Contents/MacOS/inkscape file.svg --export-filename=file.emf

Upload the EMF file to Google Drive with content type “application/x-msmetafile”.

rclone copyto --http-headers '"Content-Type","application/x-msmetafile"' file.emf gdrive:file.emf

Right-click on the file in Drive and open in Google Drawings (if Google Drawings isn’t an option, you don’t have the right content-type set on the file.

Copy from Google Drawings to Google Slides.

Enjoy your painful-but-at-least-possible vector objects in Google Slides!