I'm an experienced Reception teacher and, as most people have reassured you, behavioural changes are fairly common at the start of Reception as the children are absolutely exhausted. They're having to focus and concentrate so much on new rules and routines. Rest assured, it doesn't usually last much beyond October half term before they're more like their old self, once they have adjusted.
You seem to be making a lot of assumptions about the school based on very limited knowledge. The first few weeks are primarily about settling the children in, helping them to explore the classroom, make friends and learn to rules and routines. The teachers also have to carry out baseline assessments and best practice is not to explicitly teach new skills until these have been completed, to make them as accurate a reflection as possible of where the children are currently at upon entry to the school. This means many schools hold off teaching letter sounds for the first couple of weeks. Phonics will definitely be happening, but in the most basic forms (lots of listening games, oral blending etc). These skills are the real foundations of learning to read and spell, but a lot of parents only think of learning letter sounds as 'proper' phonics.
I understand it's a difficult transition for parents from nursery, with daily personalised hand covers, to school where you're generally not individually spoken to unless there is an issue. It would be completely impractical though for teachers to tell each individual parent about their child's day. Unlike nursery, where there are staggered pick ups, the children are all released at the same time. You'd be waiting for half an hour if you're at the back of the queue if they spoke to every parent! If the teacher hasn't needed to speak to you individually yet, that is a sign that all is going well. If you need to talk to the teacher though you can always hang around to catch them after all the children have been safely seen out to their grown ups. Reception teachers in particular are especially use to listening to queries and concerns from new parents. It's as big an adjustment for you as it is your child and we do understand that. Unless you have already tried to talk to them and they've turned you away, it's really quite unfair to criticise them for being too busy to talk to you. They are busy, incredibly busy (especially at this time of year) but that doesn't mean they won't be there to listen if you need to talk to them.
With all due respect, you are blowing the screen time thing completely out of proportion. I understand you are anti-screens but I can assure you your child will not be glued to a screen for hours on end (nor does a tiny bit of screen time mean they're not receiving a proper education). As other people have explained, it's most likely that the screen time is for no more than 5 or 10 minutes during a transition period, such as while groups are being sent to wash their hands for lunch. Or potentially at the end of the day, to 'contain' them all attentively on the carpet while the adults are safely seeing their friends out of the door. If Bluey is the last thing he's seen that day, before leaving, that's what he's most likely to remember and tell you about, even if it was only for 5 minutes.
Give the school a chance. They are not responsible for your child's change in behaviour, which is completely developmentally normal, and a tiny bit of screen time each day is definitely not an instant sign that they're not giving him a proper education. I'm sure you'll have a parents evening at some point this term, where you'll receive a full debrief on how ue has settled in.