I think screens are a reality today, but I would also get him some toys even if he doesn’t seem interested (he may have them already). Legos, blocks, toy kitchens, feeding the stuffed animals, Play doh etc. Play with him if he will sit with you, play by yourself, model the play skills, etc. even if it’s only for 3 minutes at first.
If he hyper focuses on the numbers - counts the Play doh cookies and tells you how many more to get to 50, focuses on the numbers on a toy measuring cup etc…acknowledge him and redirect to feed the animals because they are hungry, etc. Redirect to more socially appropriate conversational skills.
Being a highly gifted 8 year old is great, but it’s also important to have appropriate social skills, and that includes not always pointing out numbers on a clock, addresses on homes etc … while he’s conversing with others. His love of numbers can work in his favor when he’s doing academics, but talking with somebody about a book while saying all the page numbers (on page 27 this happened, he lives at 80 Smith Street, she lives next door so her number is 78, etc) might not always work in his favor, socially and conversationally speaking. I am not saying he does this.
There are many reasons why he might be hyper focused on numbers, why he might seem ok around strangers (more so than other toddlers?) why he doesn’t have pretend play, etc …even if he is also highly, highly gifted.
I don’t know, because I have never met him. I would not worry about middle school right now. Encourage his interests, let him explore, redirect the conversation and model what is appropriate (again, I don’t know him).
Have fun with him!! It goes by fast.