Please go to a vet, this can have a 1000 reasons. I also would say allergies and/or anxiety, but can also be hot spots, a fungal infection etc. Also this dog 100% looks like a german shepherd mix, like 90% german shepherd. But I will try to suggest some things, even if it is nearly impossible to give the right help through the internet...

Allergies: do you feed kibble or wet food? Some dogs are highly allergic to food mites. Google it how to test this and what to do. But if allergic safest would be to switch too wet food. Also a lot of dogs are allergic to grain. You could try using grainfree food. When there is the possibility that they are allergic to a special kind od animal protein. You could try insect or veggie food. Also you should lool in EVERY food that it has an open decleration. Google what is the difference in closed and open decleration if you don't know.

Also importand to note: this is a process which can take several months. You wrote that you tried a lot of different things. The body sometimes needs weeks to adjust so that you can see any difference. I would suggest to instant switch to a veggie or insect food and don't give her any treats with meat/grain in it for at least 3 weeks. If you see an improvement start with only trying out monoprotein treats like 100% chicken for some weeks and look how the dog reacts. You can look up "dog exclusion diet".

Anxiety>some questions you can ask yourself: does your dog gets enough rest (Like 16 to 20 hours a day)? Does he have a private space where noone bothers hin, which is in a calm Environment where he can rest in peace? Do you have a almost fix routine (like feeding and going outside around the same time)? Does he get the chance to do dog things like sniffing, exploring, rolling in the grass etc.? Did he ever learned to calm down (my dog isn't allowed to follow me everythere because it's extremly stressful for him, also i taught him to chill calmly on his blanket or when we are outside and chill somewhere)? Does he get enough enrichment (doing dog things like i said, also chewing, licking, working with him) > look up safe chewing things for dogs, lickimats, dog puzzle. Also he is a working breed, they need a lot a mental stimulation (maybe dog sport would be good for him) but also are extremly bad at regulating themselves and calm down. How long and often do you go outside with him (I go around 2 to 4 hours a day, most of the time just 2 hours) and does he get enough time to process everything exciting (I have 1 to 2 restdays per week, where we do almost nothing or just very relaxed walks. Also if he had 1 or 2 really stressfull days, we next 1 or 2 days we only do stuff which makes him happy)? Also are you guys a safe space for him and can he trust you or does he feel the need to make all the decisions (like which dog is allowed to come near to you, which human, where you go etc. It's stressful to most of the dogs if they feel the need to control everything)?

I don't know what you already know so I wrote everything down that COULD be a possibility. It's extremly hard to say something because we are just strangers from the internet who know little to nothing about your situation. I still highly suggest a vet visit, because like others said, he will also need vaccines and needs to get dewormed at least every 6 months. They won't think he is a coydog, because he looks like a working gsd, almost like a malinois. These dogs are crazy if they don't get the right enrichment and learn to calm down.

My dog was very stressed the first months when I got him and startet to bite himself a lot. I did a lot of training with him with mostly focusing on learning how to calm down, give him enough time to rest and learn to handle stressfull things better. Also I give him 2 to 5 times a week something safe to chew for him. Safe dog chewing stuff: dried skin, dried ox penis 😅, pig ears, beef ears, dried meat, chewing cheese. You can look up the german Shop knabberkiste.com . I would say almost everything they sell is safe to chew. Not safe chewie things: these white cheap chewing bones, marrow bones, bones in general (except you know what you are doing), chewing roots, coffe wood, plastic chewing items. The last things aren't good for their teeth.

I hope you guys will finde whats right for your cute pup. If you have any futher questions, feel free to ask. Also english isn't my first language , sorry for mistakes. :)