Yes, assets from different source are in fact quite well to handle. I use Lightroom Classic and hence will only discuss this tool in my answer. (Beware: there are 2 versions, Lightroom and Lightroom Classic - the latter having more features).
These features help me how to manage assets from different sources:
- metadata (esp. the IPTC Contact section with the Creator, Website, E-Mail fields to keep track of the source and also the Copyright section)
- colour labels
- library filters
- smart collections
I only import photos from one source at a time. I use metadata presets for different creators whose photos I import regularly. Otherwise, I just input what's needed in the metadata fields later (after import).
For every photo that is not mine, I use a colour label that is visible in the library as a background colour behind the photo thumbnail which makes them stand out. This is useful to remind me that I cannot publish them without permission. Additionally, the colour label can be used to filter easily between my work and that of others (the colour label filters are in the attribute tab of the library filters, which can be found above the gallery view).
The library filters allow you to only show photos based on certain criteria, e.g. only those from specific persons, websites, etc. - whatever has been written to the metadata.
Finally you can create smart collections that show only those photos that fulfill a number of rules that you have defined.
P.S.
Another way to separate assets is to use multiple catalogs. However, this is more complicated to handle in most cases, because Lightroom can open only one catalog at a time.