Dd was 11 and in Y5 when she was allowed to come home alone. It started when she was still 10 (just - late autumn term) walking home as I drove and building up to her leaving at 5:30, then 5:00pm, when I was due home at 5;45pm ( 15 minute walk so initially i was home at the same time more or less).
Early spring, she needed to come home at 4pm twice a week rather than go to after school club due to bullying there but really wanted that rather than going to the alternative after school club 4 days per week and missing all except an off-site ECA. (She has to drop 2 ECA’s as other after school couldn’t collect other than end of school day).
And that worked ok, so in Y6, she came home herself everyday after ECA’s, which finished between 3:30 and 4:15. I was home at 5:45.
We had built up to it when it wasn’t a problem, just building independence. She knew how to cook safely (Oven, microwave and kettle were fine but only use gas rings when I was home) from years of doing things and getting more independent in the kitchen - and I did buy things like Koka noodles (similar to Pot Noodle) that she liked as solutions for snacks when she got in. And she was pretty good at doing her homework before relaxing with tv/xbox. (Slapdash sometimes - but done). And also good at phoning me daily to say she was home safe, and not letting others in until I was home. And we had neighbours who WFH or are retired, that knew the routine and were around (And dd knew to call into) if there were problems.