I know this has been asked before, but it's been many years since I checked in, so looking for recent recs on this:

Have a family member with many (at least thousands, although we don’t have to do them all at once) negatives that they want to get scanned.

Any companies you can *personally* recommend?

@Drwave I used https://www.memoriesrenewed.com/ to scan and correct 8000+ slides and negatives of my late father and brother. The team was incredibly helpful.
I was able to get the corrected and uncorrected images in TIFF and JPEG. They duplicated the naming and numbering used on the original slides, making it very simple to add metadata from the paper photo diaries I have.
Total time door-to-door was about 4 weeks.
Memories Renewed

Memories Renewed® specializes in preserving photo and video memories so they can be enjoyed in today's digital age. We convert a wide variety of formats including photos, slides, negatives, videotapes, audio cassettes, and 8mm/16mm film.  Flexible output and viewing options are available to fit the needs of our clients.  Our studio is located in Minnesota, but we have touched the hearts of people around the world.

Memories Renewed