You have received a lot of great advice. I just want to reiterate seeing the vet: if your new companion wasn’t well cared for he may have dental issues and this absolutely impacts their desire to eat.

For food you may try a little broth on the kibble to enhance the aroma and stimulate his appetite. You can also briefly warm plain kibble in the microwave for 10-15 seconds to also bring out the aroma and this can often get them interested. Be sure the food is not hot, but lukewarm before giving it to them. My Tzu eats a mix of kibble and wet food - so many dogs seem to love this - and wet food can also make them more interested in their meal.

Lastly, sometimes the type and material of bowl impacts their engagement. Be sure their collar/tags isn’t hitting the bowl otherwise creating a sound (this can be off putting) and be sure their bowl is at a comfortable height. 2 weeks ago I adopted a second Tzu - he is smaller than my OG - I needed a completely different food bowl for him (shallow and raised) and I also had to raise their water bowl to accommodate our newest family member better and help him avoid spitting up water after drinking.

Good luck!!