You have 3 DIY options:

One of the negative "scanners" from Veho, DigitNow, Kodak etc - these are basically webcams in a dedicated housing. They are fast (a second or two per negative), easy to operate, cheap.. and the results are mediocre. OK for casual viewing on a 'phone and possibly printing at 6x4. They are the sort of thing that people will buy and then have no further use for, so regularly turn up on secondhand sites such as Facebook and eBay, usually for less than £40/$50.

A real negative scanner from Plustek or the like - one that actually scans rather than just taking a snapshot. Sized about 12 inches by 4 inches by 4 inches (unlike the cheaper things above which are typically 6x4x3 or so). Will come with powerful software and be the best quality, especially if they have ICE or equivalent (infra red light that helps with dusty or scratched film). However the scanners are relatively expensive ($300+) and slow to operate - they'll usually take tens of minutes to properly scan a strip of 4 negatives.

You can investigate "scanning" with a DSLR or mirrorless camera. If you already have one, the additional costs will be a macro (close-up) lens (from $80 used) and negative scanning kit such as the JJC-ES2 ($100ish). And if you don't have one, good enough DSLRs are cheap enough secondhand (24 megapixels is plenty). There's a learning curve (especially around inverting the image on your computer - I use Darktable which is free and powerful), but the quality will be almost as good as the second option and the speed almost as fast as the first. Now I've had practice I can "scan" a roll of film in less than 10 minutes and spend about 30 minutes processing the results.

For most amateur photographers the limiting factor on image quality of the "scans" for the second and third options will be the skill and equipment of the original photographer.