On one system I habe a debuginfod_client folder under .cache of about 10GiB. what are they and can I delete the contents?
Check [man debuginfod-client-config]. It’s a disposable directory, which keeps debuginfo data that has been downloaded and recently used.
I have no need to debug anything here. Can I stop this cache to exist in the first place? Do I need debuginfo to run my F43 workstation?
These files would have been downloaded because some tool you ran thought it needed the data. It could’ve been a profile or crashdump analyzer or something. Future uses of these tools will automatically clean off long-unused bits in the cache. Anyway feel free to nuke the directory. It’s possible to frustrate future attmepts by these tools to fetch this info (via $DEBUGINFOD_CACHE_PATH sabotage 
) but then they will fail.