The best you can do is take out the as card, copy everything to Google photos and/or Google drive, (I also copied everything I could to a 128GB USB 3 .1 flash drive) then set phone up to auto-matically copy all photos instantly to Google photos. I have also texted and emailed important ones to myself.
Out of the several hundred photos I lost when it started and through many attempts to fix the prob I think I only ever retrieved 1.(lots of my grandkids some of parents who are both deceased). So far to the best of my knowledge nothing anyone has tried worked long term.
There was a thread a few of us were on for 2 1/2 years maybe closer to 3. Some fixes will work for a few days or months even but none seem to really last. For me eventually the phone started corrupting photos in my gallery even with out an SD card in it. One a few here and there but I deleted over 147 couple months back (saved them to a seperate album to see how many)
Other backups would be Google drive a cloud account Amazon photos, if your a prime member, Roku or streaming media box if you have a comparable one, text, email or message to your self. Or if you know how burn to disks ect.
If you can connect to the old thread we had going maybe you can try some of the suggestions on there some worked for a few months at least and 1 or 2 may have worked for a few but no one reported back. Just back up and copy or send everything first. Can also use Google activity go to it and try downloading all your activity maybe some saved it there ... Just make sure you have the space it takes alot. Then copy it to something else as well.
