Hello, and welcome to the forum
If I got you right, you experience the problems with various SD-cards and not just the one you have been using for years.
You could try cleaning the contacts.
Have you disassembled the phone, to take a look at the core-module for any visible damages?
You find the pictured tear down on the iFixIT homepage.
The pictures for Step 12 and Step 13 show, how the module should look like.
The SD-card slot is located on the core-module. Should it really be broken, you could look for a used phone on the market place in this forum to switch the core-module.
Or - if it’s a case of broken soldering - you could try the “baking the module” solution in this thread:
Posting #143 / Posting #152 / Posting #169 (regard posting #171) and Posting #207 are explaining what to do. There are different methods described in the postings.