Can I send in my iPhone 5c for repair?

iPhone 5C released date September 20, 2013, is an outdated iPhone nearly 9 years.

The hardware remains old.

Consider whether it is still worth repairing.

Whether it is suitable to use as a Hotspot, that is the question.

Not sure if iPhone 5C can still be repaired. Apple certainly no longer replaces battery for iPhone 5 C.

You can ask at an an Apple Authorized Reseller in your region

See this Apple article: iPhone Battery Replacement - Official Apple Support

Getting a good Wi-Fi network for the Mac might be much better.

iPhone repair amount you use to invest in a suitable router.

See -> Recommended settings for Wi-Fi routers and access points

Recommended settings for Wi-Fi routers and access points - Apple Support

No. that device is obsolete. Apple no longer services it.

True. Though it's pretty much a distinction without a difference now, considering it's effectively not usable as a phone any more.

Actually it is listed as Vintage, not Obsolete.

True dat, you could say the cell providers and FCC obsoleted that device.